Timing is also important when loading plates. The reagents should be loaded in the same order and with the same timing as previous reagents. This is especially true of the substrate and stop solutions. This ensures that each well is exposed to substrate for the same amount of time before the reaction is stopped.
Clinically significant ANCA are predominantly of IgG class. There are reports of IgA and IgM class antibodies, but these instances are very rare.
It is important NOT to mix or substitute reagents from different lot numbers. This is not recommended as each assay kit contains reagents or components that have specific lot numbers. This ensures that all the components are performing optimally, as QC testing is performed on each specific lot. If the components are interchanged with other kits or vendors, it can result in a suboptimal performance.
Reagent stability can be affected by a number of conditions. This can be minimized by adhering to storage conditions as indicated in the product insert. Inspect reagents for signs of instability or contamination. The presence of a precipitate or discoloration in the solution is an indicator of contamination. Also avoid frothing of reagents. Do not pour reagents back into the original bottle after use; only pour off what is needed for the test. Check the expiration date to make sure it has not lapsed.
It is recommended to not use the substrate if it turns yellow as this interferes with the reaction and may result in a high background. A slight yellow color can be observed with alkaline phosphatase substrates. This slight hue is not a concern. You should only be concerned if the OD of the substrate alone goes above 0.3 OD at 405nm. Also, check the expiration date to make sure it has not lapsed as this may affect the stability of the substrate.
It is important to ensure that plate pouches are sealed correctly and undamaged. Always return any unused portion of plate as quickly as possible, as for most plates prolonged exposure to outside air can cause the solid phase to decay much more rapidly. When resealing the plate, make sure that the desiccant packet is replaced in the pouch, sealed tightly and returned to storage at 4 degrees centigrade. An unsealed pouch reduces shelf life quickly.
Washing can be optimized by using distilled or deionized water when diluting wash buffer powdered concentrate. Also check the expiration date to make sure it has not lapsed. When using an automated plate washer or manifold dispenser, be sure all pins on the wash head are clear.Why is it important to adhere to timing during the test?It is important to adhere to the timing during the test as variations may cause results to vary greatly. Check the product insert for timing and follow it closely as incorrect incubation time may result in an invalid assay.
Variations in incubation time may cause results to vary greatly. This is especially true of short incubation times. Binding will continue if the incubation time is allowed to lapse, yielding high results while shorter incubation times may cause low results. It is important to have all reagents ready so that plates can be loaded as quickly as possible, not to exceed 5 minutes. These assays were developed according to the incubation times listed in the product insert and variation will affect results negatively.
To remedy timing problems, always be ready with required equipment (pipettes, tips, test tubes, reservoirs, etc.). Also warm all reagents to room temperature prior to starting the assay so they can be used immediately (except when special conditions indicated in the product insert demand cold reagents are used at the start of 4 degree centigrade incubation period). If multiple assays are run, time each plate individually so incubation times do not lapse. Allow for washing and pipetting time by spacing assays 2-5 minutes apart.
It is important to adhere to temperature as stated in the product insert while performing the test as it is essential for accurate, reproducible results. Allow time for reagents to equilibrate to room temperature (except when special conditions indicated in the product insert demand cold reagents are used at the start of 4 degree centigrade incubation period). Cold reagents will cause lower results and uneven warming of the wells may yield an “edge effect.” If this is the case, samples located in wells toward the edge of the plate will warm faster and therefore falsely yield higher readings than those located in the center.
It is important to make certain that the laboratory and work surfaces are within the temperature range recommended in the product insert. Ensure that the room and/or incubator temperature are within the required temperature range, preferably in the middle of the range. If the laboratory is especially warm, it is recommended that a controlled room temperature incubator be used for room temperature assays. These assays have been developed based upon the given temperature range and results differ when conditions vary.
A frequently overlooked factor to consider is the temperature of the bench top on which the assay is being performed. For example, if the laboratory has heat turned down or off overnight, the temperature of the bench top will remain lower than the air temperature for some time after the heat is turned on. A cold bench top will cause the signal to be much lower and may contribute to the “edge effect.” Also locations near heat sources, in direct sunlight or close to warm equipment will cause the bench top to warm and may affect results.
“Edge effect” occurs when the reagents or ambient temperatures are colder than that specified in the product insert. This causes uneven warming of the wells and hence, the samples located in wells toward the edge of the plate will warm faster and therefore falsely yield higher readings than those located in the center.
Important during the processes of loading plates with calibrators, samples and reagents and making sample dilutions. Some of the processes that can increase the accuracy and precision of an ELISA assay are –
– Do not use pipettes below or above the recommended volume range of the manufacturer as they are not designed to be accurate outside of the range.
-Ensure that any pipettes being used are calibrated properly.
-Read the product insert carefully.
When dispensing a reagent or serum out of the pipette tip, some liquid adheres to the inside of the tip and the full volume is not dispensed, especially with viscous solutions. To avoid this, draw the reagent or serum up into the pipette tip and, keeping the tip immersed, successively eject to the first stop of the pipette, and then proceed to draw the reagent back up. This effectively rinses the pipette tip. The liquid can then be dispensed accurately by ejecting only to the first stop of the pipette. Successive uses of this pipette tip(s) for the same reagent or sample do not require additional rinsing. It is important not to scratch the bottom of wells when dispensing reagents onto the micro titer plate. Place the pipette tip on the side of the well to prevent droplets from remaining on the end of the tip, while avoiding contact with the bottom of the well. Take care to press pipette tips firmly onto the pipette. Check tips visually to be sure that liquids are being dispensed and aspirated completely.
To avoid cross-contamination, do not drag pipette tips over into other wells. Always use separate reservoirs and change pipette tips with each new reagent. Always use clean tips. Avoid mixing reagents.
When pipetting and loading the micro titer plates, it is important not to scratch the bottom of the well with the pipette tips. Avoid cross-contamination and pipette slowly to prevent bubbles in the pipette tip due to turbulence. These bubbles will prevent liquid from being dispensed completely when the pipette is ejected to its first stop. After loading is complete, gently agitate plates briefly to be certain that all of the liquid in each well is at the bottom. An air pocket may form at the bottom of a well due to the surface tension of the liquid. Brief agitation will eliminate this.
It is important to choose the location of your plate carefully. Do not move or agitate plates during incubation. Also avoid areas of high intensity and stay away from air currents or machines that radiate heat.
An incubator set to the middle of the given temperature range is an ideal location for ELISA plates. Read the product insert for incubation temperature for the assay.
It is important to avoid moving or agitating the plates during incubation as this may cause the reagents to spill out of the wells and may increase development rates. Be sure to avoid areas where other workers will bump or move plates.
Do not incubate plates in areas of high intensity. Avoid placing plates near air vents or other objects such as refrigeration units that will emit warm or cool air. Direct exposure to sunlight will increase the temperature of the plate or the reagent. Enzyme substrate is also light sensitive and backgrounds will increase if the plate is exposed to light during the substrate incubation period.
It is recommended to use an automated plate washer for the wash steps to ensure that complete and even amounts of wash buffer are administered. Check for clogged pins in the wash head, rinse with deionized water if necessary. Also, decontaminate the washer weekly or monthly. After washing, invert plate and tap on an absorbent paper towel. Tapping technique is a critical step in the washing process. Firmly tap plates before adding new reagents. The number of repetitions necessary depends on how firmly or gently the plates are tapped. For example, more repetitions are required when gentle tapping is done. Check the product insert for information about which method is appropriate for your particular kit. Always visually check the plate for remaining liquid. More tapping may be necessary if liquid is remaining in the wells. After washing, proceed to the next step immediately to avoid drying out the plate. If an automated plate washer is not available, manual washing may be done.
Freshly drawn and properly refrigerated serum, and in some cases, plasma (read product insert) can be used for this assay. Do not use icteric, hemolyzed, grossly lipemic, or specimens with obvious microbial contamination. These may cause false reactions and strips are unreadable. Plasma may be used in the ANA Western Blot Immunoassay, but serum is preferred as the risk of cross contamination and false positives are high.
Samples can be stored at 2-8 degrees centigrade for 3-5 days or at -20 degrees centigrade or lower for longer periods. Avoid repeated freezing and thawing of samples. Optimum conditions for specimen handling are provided in the product insert.
Each assay kit and its components have recommended storage temperatures that are stated on the label and product insert. Read the label/product insert for the recommended storage condition. Most of the reagents can be stored refrigerated at 2-8 degrees centigrade. Do not freeze. All reagents must be brought to room temperature (22-30 degrees centigrade) prior to use.
This is not recommended as each assay kit contains reagents and components that have specific lot numbers. This ensures that all the components are performing optimally as QC testing is performed on each specific lot. If the components are interchanged with other kits or from other vendors, it may result in a suboptimal performance.
All kits have an expiration date and are clearly marked on the kit box label and individual components. In order for the kit to perform optimally, it should not be used past the expiration date.
The kit expiration date may not be the same as the expiration dates on the individual reagents. The reagents may have an expiration date that may exceed the kit expiration date and vice versa. This is because when the components are manufactured, they are stored in-house under different conditions, and hence the individual reagent expiration dates reflect this alternate storage. The kit expiration date is assigned for optimal performance of all reagents when stored at the temperature recommended on the labels.
Strong bands on a Negative Control strip may be due to contaminated negative control or due to cross contamination from a well containing a positive control or serum.
A positive control can appear as a negative control or with no color if the control was not added (omitted) or if the positive control vial was confused with the negative control. This may also result if the control is pipeted incorrectly (see product insert).
The strips may appear completely blank if the conjugate or substrate was omitted. No color will develop if the proper volume of reagents were not added, incubation time and temperature was not observed. This may also occur if the strip was not adequately shaken or the reagents were not brought to room temperature prior to use. Also, please refer to the product insert for tips on good technique to avoid common mistakes, or contact IMMCO technical service department for assistance.
Weak color development may be due to a number of reasons for example, if substrate, antibody and conjugate were not added at the correct point in the assay. Also it is important to use all the components that belong to the specific kit used. Interchanging components with different kits can result in false test results. Incubation times also play a role. Bands may be lower in intensity and color, than expected if the optimum temperature is not used, for example, if the strip was left to incubate on a cold bench or drafty area during ambient incubation. It is also important that all reagents are brought to room temperature prior to use (see product insert). Usually, leaving the kit out on the bench for about half an hour before setting up the assay is sufficient when the reagents have been stored at 4 degrees centigrade. DO NOT freeze reagents.
The most likely cause for high background and poor contrast is improper washing. Complete washing of the strips between incubations is crucial to obtain valid results. (see product insert). Also adding too little Wash Buffer can result in high background, while adding too much is not a problem. High background could also result if the strip was incubated for too long or at a higher than recommended temperature. The incubation time in the substrate can have an effect, i.e. longer substrate incubations can result in a higher than normal background. This should be monitored closely and the reaction stopped when the controls have reacted to a useful degree (see Product Insert). Also, proteins present in the patients serum may interfere and cause a high background. We recommend to ultra centrifuge the serum and retest. Please contact IMMCO technical service department for any assistance.
It is recommended that the sample volumes not be altered (see product insert). Assay kits are designed for optimal performance at the recommended volumes. In case a smaller volume of the sample is used, then the substrate and conjugate should be reduced by the same factor. The use of non-recommended volumes can alter the test results.
Fluorescence microscopy contrast can be affected by signal to noise ratio. Some of the sources that can increase noise and weaken the signal are: -Unwanted light source. This is the amount of light illuminating a sample that passes through the slide and cover slip or room light. -Vibrations that may arise due to other equipment or air ducts. -Cleanliness of the microscope. -Using an objective that is not specifically designed for high performance. -Using a port that does not give the optimal transmission for green. -Using a filter that does not maximize the number of sample photons collected. – If the illumination time is not minimized.
Background noise can be reduced by minimizing the sources that cause it. This can be achieved by the following:
Photo bleaching is the chemical destruction of fluorescent molecules as a result of excitation, fluorescence, microscopy, photo bleaching, and testing”
Photo bleaching can be controlled by several means:
Fluorescence, Microscopy, Photo Bleaching & Testing”
Prozone phenomenon usually occurs in specimens with high titer antibodies. In immunofluorescence (IFA) testing, when an undiluted or relatively low dilution sample with high levels of specific antibodies produces a negative or weak reaction it is known as prozone phenomenon. Unless the laboratory utilizes an appropriate procedure to screen for prozone, many of these cases would be reported as false negative. Laboratories may guard against prozone by screening specimens at two dilutions, one at the typical screening dilution and one at a two-fold to four-fold dilution greater. Prozone occurs in specimens with high titer antibodies. If prozone is present, the higher screening dilution produces greater (positive) specific fluorescence than the lower screening dilution, which may appear weak, difficult to read or negative.” “fluorescence, microscopy, prozone, testing”
IMMCO supplies conjugates in two formats: one with no counterstain and one containing an optimized formulation of Evan’s Blue counterstain. IMMCO does not recommend adding counterstain to the vialed conjugate contained in the kits because this approach is very imprecise with the low volumes involved. The approximate volume of counterstain that would need to be added to the conjugate is approximately 0.02 ml. IMMCO instead recommends purchase of conjugate with counterstain (either separately or with the kit) or addition of counterstain to the reconstituted wash solution as indicated in the instructions for use. “IFA, counterstain, conjugate, testing”
Some of the conditions that might impact IFA testing are :
However, stability studies have shown autoantibodies to be stable at room temperature for one month or more. Requests for other types of specimens are indicated in the special test request form and product insert.
Refer to the individual Test Request forms. A specimen is unacceptable if the vacutainer tube/vial used for collection of serum/biopsy is inappropriate, proper biopsy site for various tests and conditions are not met with. If the blood is hemolytic / icteric it is unacceptable as it interferes with the fluorescence.
Specimen processing can be delayed if all applicable areas are not filled out on the requisition form. This includes :
patient information, insurance/billing information, specimen collected incorrectly (refer to test request form), physician information, test code, clinical information if applicable. IMMCO Diagnostics is committed in providing quality services and will make all efforts to try and resolve matters efficiently and as quickly as possible.
There are a number of possible reasons, for example, the protocol was not followed, reagents were not added in order, all reagents were not added, for example, if the conjugate is missed there will be no fluorescent reaction, incubation times are not followed. Also, make sure that the microscope is calibrated properly; the technician may be new to reading IFA. These problems are generally addressed by following good laboratory practices such as regular microscope calibration and internal standardization of new assays with known positive and negative controls.
There are a number of possible reasons, for instance, the microscope may not be calibrated properly, the technician may be new to reading IFA slides, a non-specific fluorescence may be confused with specific fluorescence, there may be infiltration of a positive control or specimen into the well. These problems are generally addressed by good laboratory practices, such as calibration of the microscope, use of correct IM filters, standardization of new assays with known positive and negative controls, “”IFA, results, testing”
In such a case, check to make sure that the microscope is properly calibrated and the filter is adequate. If the fluorescent light is too strong it may enhance the intensity. Generally this can be resolved by checking the microscope for proper calibration, filters and light intensity. Also, check the reagents supplied in the IMMCO Diagnostics Kits. Technicians may review the product inserts on tips on good technique to avoid common mistakes””IFA, results, testing”
Calibration of microscopy systems may be facilitated by use of Optical Standard slide .IMMCO Diagnostics supplies calibrators such as the IMMCO Diagnostics Optical Standard slide. “calibrate, microscope, IFA, testing”
Some of the common problems that can occur are : “problems, IFA, testing” ” Reagents running off of wells,” “If this occurs use blotters to prevent runoff, dry the slide before reaction occurs, and while washing shake off the excess water. If using automatic washers make sure it is dispensing properly otherwise the well is not going to get a nice bead on the slide. ” Reaction looks different in different sections of the well. “This may be due to the conjugate or other components running off the well or the dispensing is not appropriate, which effects the beads in the wells .”
Refer to IMMCO Atlas at www.IMMCO Diagnostics .com for examples of positive reactions.”atlas, reaction, testing, IFA”
Refer to Interpretation Of Results in the Products section on the website www.IMMCO Diagnostics.com
Antibodies to specific antigens are present both in serum and in plasma, so the assay can be used for either sample. However, the sample dilution has to be optimized for serum.
“Flurochromes are highly resonant molecules with fluorescent properties. Upon illumination with a suitable wavelength of excitation the fluorescent molecules absorb energy to an excited state. On relaxation of the excited state, fluorescence is produced by radiative transition to the resting or the ground state. As the fluorochrome has the property of emitting fluorescence on excitation, it can be directly examined under the fluorescent microscope. “
Photobleaching is one of the characteristics and limitations of fluorescence microscopy as the fluorescent preparations may fade on irradiation. The mechanism of photobleaching is not entirely known. Some of the factors may include: -photochemical decomposition involving oxidative and non-oxidative mechanisms. -“the rate at which photobleaching occurs may be dependent on the characteristics of the fluorochrome. Some undergo rapid photobleaching, whereas others are relatively stable.”
IMMCO mounting medium has been optimized to minimize photobleaching. It is formulated with antifading agents to best preserve fluorescence.
The fluorescence observed on examination under the fluorescence microscope are as follows: -Desired or Specific staining: This is true staining as a result of antigen/antibody reaction. The intensity of the reaction depends upon the antigen/antibody concentration and the degree of the antibody to the flurochrome (fluorescein/protein ratio). -Undesired but Specific staining: This type of reaction may be due to the presence of cross-reactive antibodies in the conjugate to the tissue substrate other than to the target antigen. This can be minimized either by using affinity purified conjugates to the target antigen or by absorption of conjugate with cross-reactive antigen. -“Autofluorescence: this is due to the presence of natural substances in the specimen that fluoresce on excitation with UV light. Sometimes this may conceal or be confused with specific fluorescence. In tissue sections, collagen and elastic fibers quite often exhibit this phenomenon. Examination of sections unstained may help to distinguish autofluorescence from other types of fluorescence.” -Induced fluorescence: This refers to the conversion of a nonfluorescent substance in the tissue into a fluorescent compound by treatment with a nonfluorescent reagent. Formaldehyde-induced fluorescence is the most common example of this phenomenon. -Non-specific staining: This is attributed to the hydrophobic and ionic interactions of highly fluorescinated conjugate with the antigenic substrate.
“Counterstain is a reagent used to minimize non-specific fluorescence. It may be present in the conjugate or as a separate component. Unless otherwise requested, IMMCO provides conjugate with Evan’s Blue counterstain added to the formulation. If desired, IMMCO can provide conjugate and counterstain as separate components. When used as a separate component, the technician adds 2-3 drops of Evan’s Blue counterstain in the final wash buffer.”
IMMCO supplies conjugate IMMCO provides conjugates in two formats: one with no counterstain and one containing the counterstain volumes involved. The approximate volume of counterstain that would need to be added to the conjugate is approximately 0.02 ml. IMMCO recommends the use of conjugate with counterstain
“It is possible that certain conditions may have an impact on IF test results. Such conditions include specimen storage, condition of the specimen (hemolytic, icteric, contaminated sera). In general, auto antibodies are durable and serum samples will provide reliable results if stored under proper conditions (limited exposure to temperature extremes, long term storage at 2-8ºC or frozen, avoidance of multiple freeze/thaws). Improper storage will lead to degradation of the specimen over time. Cross-reactivity in the assay has been tested using disease control specimens and normal human sera. Any known cross-reactivity has been listed in the product insert. It is not recommended that compromised sera (e.g., grossly hemolyzed, icteric, microbially contaminated) be used in the immunoassay. “
“In immunofluorescence (IF) testing, when an undiluted or relatively low dilution sample with high levels of specific antibodies produces a negative or weak reaction it is known as prozone phenomenon. Unless the laboratory utilizes an appropriate procedure to screen for prozone, many of these cases would be reported as false negative. Laboratories may guard against prozone by screening specimens at two dilutions, one at the typical screening dilution and one at a two-fold to four-fold dilution greater. Prozone occurs in specimens with high titer antibodies. If prozone is present, the higher screening dilution produces greater (positive) specific fluorescence than the lower screening dilution, which may appear weak, difficult to read or negative.”
-Test protocol not followed (e.g. reagents not added in order or all fail to add one of the reagents). If the conjugate was omitted, for example, there will be no fluorescent reaction.” -Incubation time guidelines were not followed. Certain tests require longer incubation timed (e.g. overnight 18-24 hour incubation). -The fluorescence microscope is not adjusted or calibrated properly. Make sure the proper light source and filters are being used. Such problems are generally addressed by following good laboratory practices such as development of training and maintenance procedures including regular microscope calibration and internal standardization of new assays with known positive and negative controls. IMMCO offers optical standard (OS) slides to facilitate calibration of fluorescence microscopes.
There are a number of possible reasons, including: -Technician training. Technicians inexperienced in the reading of IFA slides, non-specific fluorescence may be confused with specific fluorescence. The technician must be looking for fluorescence related to a specific reaction pattern rather than general, visible fluorescence.” -Infiltration of a positive control or positive specimen into the wells of other specimens. Generally, specimens and controls form a bead on the slide surface and remain within the well. Technicians should be alert to the fact when samples flow beyond the boundaries of their well and into others it may cause a positive result through cross-contamination. -Poor washing / cross contamination. IMMCO recommends a rinse in a fresh beaker of wash buffer followed by a soak in a coplin jar for 10 minutes. These wash buffers should be replaced between assay runs to eliminate potential for cross-contamination.
Some of the common problems that can occur are: -Reagents run of from wells of the slide. Make sure the reagents are confined to the wells at each step and there is no run off. To ensure this IMMCO recommends wiping around the wells after each wash with a kim wipe or the use of a blotter. These blotters could be obtained from IMMCO. If using instrument for dispensing make sure it is dispensing properly within the well with complete coverage of the area of the substrate. -Reactions are variable from well to well. This may be caused by reagents running off the well or not being distributed throughout the well. It may also be caused by cross-contamination of specimens and/or controls from one well to another well on the slide. -Background high. This may be either associated with the serum. Some lipemic or incompletely defibrinated serum samples result in high backgrounds. Other reason could be due to incomplete washing of the slides.
Descriptions of reaction patterns are indicated in the product insert and positive controls are provided with kits to present an appropriate reaction pattern, however, the controls provided in the kit may not represent all the reactions that could be observed on a particular substrate. To help with identification of specific fluorescence reaction patterns on a given substrate you may contact our technical services department that may be able to provide images of other reactions. In addition you may visit IMMCO web site for help.
The two different methods employed in immunofluorescence are: direct immunofluorescence (IF) and indirect IF. “Direct IF is generally used for immnunopathological examination of skin, kidney or other tissues for the detection of in vivo bound immune deposits.” Indirect IF is used routinely for detection of circulating antibodies in the serum of patients with various autoimmune disorders.
A fluorescence microscope is basically a conventional light microscope with added features and components. It uses higher intensity light to illuminate the sample. “fluorescence, microscopy, IF, testing” “This light excites fluorescence molecules in the sample, which then emit light of a longer wavelength. The light emanating from the fluorescent molecule” is green for FITC. “Fluorescence microscopy is used routinely for studying the distribution of substances present in small amounts in the tissues, serum and other body fluids. Immunofluorescence microscopy is simple and, in the clinical laboratory, it is the mainstay for detecting small amounts of auto antibodies. In fluorescence microscopy the specimen to which a fluorochrome is bound is illuminated with light of a short wavelength, part of this light is absorbed by the specimen and remitted by fluorescence at a wavelength that is longer than that of the incident light. In order to visualize the fluorescence under the microscope the incident light is filtered out by a secondary set of filters, known as barrier filters, which are placed between the specimen and the eye. The resulting fluorescence is green if the flurochrome used is FITC.”
“The disadvantages of fluorescence microscopy are that it requires a fluorescence microscope, requires expertise in reading the slides and the fluorescence fades upon illumination (photobleaching).”
ANCA stands for ant-neutrophil cytoplasmic antibodies. These antibodies can be visualized using immunofluorescence techniques to react human sera on human polymorphonuclear neutrophils (PMN) as a substrate. Refer to the ANCA product insert for the proper procedure. These antibodies are associated with certain autoimmune vasculitic and gastrointestinal disorders. These antibodies target a number of antigens and produce reaction patterns based on the specificity of the reaction. The types of immunofluorescence reactions that may be visualized on human polymorphonuclear neutrophils (hPMN) cells include cytoplasmic (cANCA), perinuclear (pANCA), atypical pANCA, ANA, and negative reactions.
ANCA are markers for various vasculitic disorders including: -Wegeners granulomatosis -Microscopic polyangitis -Churg Strauss syndrome ANCA are markers for inflammatory bowel disease (IBD) including: -Crohn’s Disease -Ulcerative Colitis ANCA are present in hepatobilliary disorders such as: -Primary sclerosing cholangitis -Autoimmune hepatitis “ANCA help to differentiate various subtypes of vasculitis. cANCA is found preferentially in Wegener’s granulomatosis (small blood vessel vasculitis with respiratory tract involvement), while pANCA is found in Microscopic polyangitis and Churg-Strauss syndrome. ” “The levels (titers) of ANCA in patient serum are indicators of disease activity. They are therefore useful in predicting the disease progression and severity, and in monitoring the efficacy of treatment. Early detection of ANCA has therapeutic significance as it may lead to effective early treatment.”
Neutrophils a type of white blood cell that constitute 60-75% of the total white blood cell population. The other major white blood cell is the lymphocyte which constitutes 20-45%. The remaining white blood cells (basophils, monocytes and eosinophils) together constitute less than 10%.
ANCA react to various antigens of the neutrophils and are associated with vasculitis, inflammatory bowel disorders, autoimmune hepatitis, and primary sclerosing cholanagitis. The antigens are primarily associated with alpha granules in the cytoplasm of the neutrophils and monocytes.
cANCA and pANCA are associated with vasculitis. Atypical pANCA is associated with IBD, primarily with ulcerative colitis.
Vasculitis is inflammation of blood vessels affecting small, medium and large blood vessels. The commonly affected area of the body is skin (cutaneous vasculitis), however, it may also affect other organs such as kidney, lungs, etc. (systemic vasculitis).
Cutaneous vasculitis causes a skin rash, papules and pain. Systemic vasculitis may cause general symptoms such as not feeling well, weight loss, and joint pain.” -Any organ may be affected by vasculitis. When kidney is involved, blood and protein may appear in the urine. -Weakness and numbness of the hands and feet may be caused by inflammation of blood vessels. -Abdominal pain and bleeding. -Vasculitis affecting the myocardium may result in symptoms similar to a heart attack. In the brain, vasculitis may cause a stroke.
Initial screening of suspected vasculitis patients is performed by laboratory testing for ANCA by IFA in patient sera. In addition, the following may be observed: -Erythrocyte sedimentation rate (ESR) is generally elevated. -Complete Blood Count will often show anemia, elevated white cell and platelet counts. -Urinalysis to screen for kidney involvement. Kidney biopsies are helpful if there are indications of kidney involvement. -Angiograms can help diagnose vasculitis affecting large blood vessels.
The close association between ANCA levels in serum and disease activity suggests a patho-physiological role for ANCA.
cANCA are predominantly present in patients with Wegener’s granulomatosis, whereas pANCA are predominantly present in patients with Microscopic polyangitis and Churg-Strauss syndrome.
No. If the patient is suspected of vasculitis, the patient sera can be screened by testing on ethanol fixed neutrophils for the presence of cANCA or pANCA. If pANCA are observed they can be easily confirmed by testing the sera on formalin fixed neutrophils.
Three types of ANCA reactions are observed on the neutrophils. These include cytoplasmic (cANCA); perinuclear (pANCA) and atypical pANCA. In addition antinuclear antibodies (ANA) also provide nuclear reactions on the neutrophils.
Cytoplasmic reactions on ethanol fixed slides indicate the presence of cANCA antibodies. A sample positive control reaction appears at right. Note that the hPMN cells produce a fluorescent reaction of the cytoplasm of the cell while the lobes of the nucleus are dark (A). Lymphocytes are negative (B). In this image, the lymphocyte has been enhanced to make it more noticeable. ” cANCA antibodies reacted on formalin fixed slides also produce a cytoplasmic pattern. “The primary antigen targeted by cANCA antibodies is proteinase 3 (PR3). PR3 antibodies are associated with vasculitic disorders such as Wegener’s granulomatosis, microscopic polyarteritis and Churg-Strauss syndrome. Other cANCA specificities include bactericidal permealizing increasing factor (BPI) (5%). While the disease association of PR3 and BPI have been established, certain specificities of cANCA may not have clinical relevance.”
Perinuclear reactions on ethanol fixed slides may indicate the presence of pANCA antibodies or anti-nuclear antibodies (ANA). A sample positive control reaction appears at right. Note that the hPMN cells produce a fluorescent reaction around the multi-lobed nucleus (A). Lymphocytes are negative (B). In this image, the lymphocyte has been enhanced to make it more noticeable.” “pANCA, perinuclear, testing” “It may be difficult to discern the reaction pattern of pANCA from ANA. A model ANA reaction on ethanol fixed hPMNs appears at right (C). The reaction is similar to the pANCA pattern and may be more intense depending on the titer of the ANA. Note the lymphocytes are positive (D). While the reaction may differ somewhat from pANCA and one can see a difference in the reaction of lymphocytes present, we do not recommend differentiating pANCA from ANA using the ethanol fixed hPMN substrate alone. Specimens that produce a perinuclear reaction on ethanol slides should be tested and compared with their reactions on a formalin fixed hPMN substrate.” “A reference reaction for pANCA on formalin has been provided at right. On a formalin fixed substrate, pANCA reactions become cytoplasmic (E) while ANA reactions become weak or negative. Note the lymphocytes remain negative (F). Comparison of reactions on ethanol and formalin fixed substrates is the best method for discriminating between pANCA and ANA. One may also consider reacting ANA positive reactions on HEp-2 cells to determine the titer and specificity of ANA. ” “The primary antigen targeted by pANCA antibodies is myeloperoxidase (MPO). MPO antibodies are associated with a variety of immune mediated diseases, including microscopic polyarteritis, ” “necrotizing and crescentic glomerulonephritis, Churg-Strauss syndrome, polyarteritis nodosa,” “Wegener’s granulomatosis and chronic inflammatory bowel diseases. Other cANCA specificities include elastase, cathepsin G, and lactoferrin.
The pANCA reactions are considered artifacts of ethanol fixation of neutrophils. Upon ethanol fixation the positively charged pANCA antigen migrate and associate with the negatively charged nucleus. This results in a perinuclear reaction.
The pANCA reactions can be distinguished from ANA reactions on formalin fixed neutrophils. On formalin fixed neutrophils the pANCA reaction will convert to a cytoplasmic reaction, whereas ANA reactions will stay nuclear and are either diminished or disappear. Use of formalin (a crosslinking fixative), prevents the migration of the cytoplasmic granules towards the nucleus and thus, pANCA reactions appear cytoplasmic. ” “pANCA, reaction, patter, testing” Samples with pANCA reaction patterns may also be tested on HEp-2 cells to identify specific ANA reactions.
Atypical pANCA, sometimes referred to as “xANCA,” is a distinct perinuclear ANCA pattern characterized by an uneven perinuclear or “snowdrift” pattern and negative by MPO ELISA. Atypical pANCA is present in cases of inflammatory bowel disease. Approximately 80% of ulcerative colitis (UC) patients and 25% of Crohn’s disease (CD) patients are positive for atypical pANCA. In conjunction with testing for anti-saccharomyces cerevisiae antibodies (ASCA), atypical pANCA IFA is a powerful tool for discriminating cases of UC from CD.
xANCA is another name for atypical pANCA.
The two primary techniques used for fixation
Lymphocytes are present to help a technician distinguish between ANCA and ANA reactions. Patient sera that are positive for cANCA or pANCA but negative for ANA will not produce a fluorescence reaction on the lymphocytes while ANA positive sera will produce a fluorescence reaction on the lymphocytes.