INFECTIOUS MONONUCLEOSIS TESTING *

Effective Date: 
Tue, 05/01/2007
Reviewed: 
Wed, 05/23/2018
Revised: 
Wed, 04/25/2018
Policy: 

Method: McKesson Consult Mononucleosis Tests Cassette

CLIA Complexity: Whole blood, Waived

Principle:

McKesson Consult® Mononucleosis Cassette one-step antibody test for infectious Mononucleosis uses direct solid-phase immunoassay technology for the qualitative detection of IM heterophile antibodies in whole blood.  For  whole blood, 25 L of blood is collected in a sample transfer pipette and added to the Sample Well (S). If any IM-specific heterophile antibody is present in the sample, it will be captured by the antigen band (bovine erythrocyte extracts) impregnated in the test membrane. The developer solution is then added in the Sample Well (S). As the specimen followed by the developer moves by capillary action to the antigen band, the solution mobilizes the dye conjugated to anti-human IgM antibodies. Visualization of the antigen band at the Test position (T) in the result window will occur only when the IM-specific heterophile antibody binds to the extracted antigen obtained from bovine erythrocytes. As the antibody-dye conjugate continues to move along the test membrane, it will bind to another band located at the Control position (C) to generate a colored band regardless of the presence of IM heterophile antibodies in the sample. Therefore, the presence of two colored bands, one at the Test position (T) and the other at the Control position (C), indicates a positive result, while the absence of a colored band at the Test position (T) indicates a negative result.

Materials:

25 McKesson Consult ® Mononucleosis Cassette Test Devices containing a membrane strip coated with bovine erythrocyte extract and a pad impregnated with the monoclonal mouse anti-human IgM antibody-dye conjugate in a protein matrix containing 0.1% sodium azide.

• 1 Developer Solution: Phosphate saline buffer containing 0.1% Sodium Azide as preservative.

• 1 Negative Control: Diluted Human Serum containing 0.1% Sodium Azide as a preservative. For periodic use as external control material.

• 1 Positive Control: Diluted Human Serum containing IM heterophile antibodies and 0.1% Sodium Azide as a preservative. For periodic use as external control material.

• 25 (10 μL) (black line) sample transfer pipettes for use with external contols.

• 25 (25 μL) (red line) sample transfer pipettes for use with whole blood.

• 1 Instructional insert

• 1 Procedure card

PRECAUTIONS

• The reagents in this kit contain sodium azide. Sodium azide may react with lead and copper plumbing to form highly explosive metal azides. Upon disposal, flush with a large amount of water to prevent azide buildup.

• All patient samples should be handled as if they are capable of transmitting disease. Observe established precautions against microbiological hazards throughout all procedures and follow the standard procedures for proper disposal of potentially infectious specimens.

• Human blood and its products are potentially infectious; handle with appropriate precautions.

• For in vitro diagnostic use. Do not use after expiration date.

• Do not interchange reagents from different kit lots or use beyond the expiration date. The reagents in each kit are tested by Quality Control to function as a unit to assure proper sensitivity and maximum accuracy.

• Use only in accordance with instructions supplied with the kit.

SPECIMEN COLLECTION AND PREPARATION

WHOLE BLOOD

Anticoagulated Blood: Whole blood collected in CPDA-1, heparin or EDTA can be used. Mix whole blood by inversion and use in the test as outlined in the Test Procedure. Whole blood can be stored at 2°- 8°C for 24 hours. If testing is anticipated after 24 hours, separate plasma as outlined below and freeze at or below -20°C.

Caution: Do not freeze and thaw whole blood; hemolyzed blood cannot be used in this test

Specimen Storage - Refrigerate all specimens at 2°- 8°C until ready for testing. Specimens should not be repeatedly frozen and thawed.

 

 

 

Procedure: 

PROCEDURAL NOTES

• The test protocol must be followed in order to achieve optimal test reactivity with specimens. Follow the assay procedure and always perform the test under carefully controlled conditions

• Allow McKesson Consult ® Mononucleosis Cassette Test devices, reagents and specimens to equilibrate to room temperature before testing

• The McKesson Consult ® Mononucleosis Cassette Test device should remain in the sealed pouch prior to testing.

• To avoid cross-contamination, use a new, disposable sample transfer pipette for each specimen

• Label the device with the patient’s name or sample number

• To add the Developer Solution, hold the dropper bottle in a vertical position above the LOWER END of the Sample Well (S) and dispense 2-3 drops in the well

• Mildly hemolyzed whole blood specimens do not affect the test result, but may create an undesirable reddish background in the result window

• To avoid contamination, do not touch the tip of the Developer Solution dropper bottle to skin or McKesson Consult ® Mononucleosis Cassette Test device

• Use accepted microbiological practices for proper disposal of potentially infectious test materials and disinfection of contaminated equipment

• After testing, dispose of McKesson Consult ® Mononucleosis Cassette Test devices, and sample

DIRECTIONS FOR USE OF SAMPLE TRANSFER PIPETTE

The sample transfer pipette has an air vent positioned on the sidewall of the pipette to provide automatic air venting and sample volume control.

Note: Once the specimen is drawn into the sample transfer pipette, the pipette will not leak; the pipette will hold the specimen until the bulb of the pipette is squeezed.

Caution: Filling is automatic: Do not squeeze the sample transfer pipette while filling. Avoid air bubbles.

STEP 1

Hold the sample transfer pipette horizontally and touch the tip of the pipette to the sample. The specimen can be obtained from vacutainer or test tube. Capillary action will automatically draw up the correct volume to the fill line and stop.

STEP 2

To expel sample, align the tip of the pipette over the upper area of the Sample Well (S) of the test device and squeeze the bulb.

Note: If a sample does not expel, hold the pipette vertically and place a finger over the vent hole. Then align the pipette tip over the upper area of the Sample Well (S) of the test device and squeeze the bulb.

TEST PROCEDURE

STEP 1

Remove a test device from its pouch and place on a flat surface.

STEP 2

Collect the sample using the appropriate sample transfer pipette according to the volume of sample required.

For whole blood samples, use the 25 μL (red line) sample transfer  pipette. For control samples, use the 10 μL (black line) sample transfer pipette. Follow the directions for sampling using the sample transfer pipette.

STEP 3

Add 2-3 drops of Developer Solution into the lower area of the Sample Well (S).

STEP 4

Read the results at 8 minutes. Do not read test after 15 minutes.

 

INTERPRETATION OF RESULTS

POSITIVE

One pink-purple colored horizontal band each at the Test position (T) and at the Control position (C) indicates that IM-specific heterophile antibodies have been detected.

NOTE: A positive test result may be read as soon as a distinct pink-purple colored band appears at the Test position (T) and at the Control position (C). Any shade of pink-purple colored horizontal band at the Test position (T) should be reported as a positive result. The intensity of the colored band at the Test position (T) may be different from the intensity of the band at the Control position (C).

NEGATIVE

One pink-purple colored horizontal band at the Control position (C), with no distinct colored horizontal band at the Test position (T) other than the normal faint background color, indicates the IM-specific heterophile antibodies have not been detected.

INVALID

A distinct colored horizontal band at the Control position (C) should always appear. The test is invalid if no such band forms at the Control position (C).

McKesson Consult ® Mononucleosis Cassette Test is optimized to have a minimal prozone effect. Therefore, specimens containing a very high titer of antibody may produce a somewhat weaker signal but would still produce a positive result. The test does not require any specimen dilution, but it is recommended that the specimen be diluted and retested to confirm the result in case a prozone effect is suspected. The test should be used only for the qualitative detection of heterophile antibody.

 

Quality Control:

Internal Procedural Control

 

There are two internal control features in McKesson Consult ® Mononucleosis Cassette Test. A colored control band will always appear at the Control position (C) if the test has been performed correctly and if the device is working roperly. This is considered an internal positive procedural control. A clear background in the result window is considered an internal negative procedural control. If the test has been performed correctly and McKesson Consult ® Mononucleosis Cassette Test is working properly, the background in the result window will be clear, providing a distinct result.

 

External Quality Control

For waived whole blood testing run an included positive and negative control with each new lot, new shipment or new operator and record in testing log. Use the 10μL (black fill line) transfer pipette when testing external controls and  proficiency survey samples.

If the controls do not perform as expected or the colored control band does not appear at the Control position (C), contact Technical Service at (877) 866-9335.

Limitations

• The results obtained by this kit yield data which must be used only as adjunct to other information available to the physician.

• Although most patients will have a detectable heterophile antibody level within three weeks of infection, occasionally a patient with strong clinical signs of IM may take longer than three months to develop a detectable level.  If further testing is desired, collect additional specimens every few days and retest.

• Some segments of the population who contract IM do not produce measurable levels of heterophile antibody. Approximately 50% of children under 4 years of age who have IM may test as IM heterophile antibody negative. EBV-specific laboratory diagnosis may be helpful in these cases.

• Some individuals are reported to maintain a low but persistent level of heterophile antibodies long after their primary illness. Heterophile antibodies have been detected in blood specimens taken more than one year after the onset of the illness.  Such false positive test results occurring in 2-3% of patients can be excluded by EBV-specific serology.

• The IM heterophile antibody has been associated with disease states other than IM, such as leukemia, cytomegalovirus, Burkitt’s lymphoma, rheumatoid arthritis, adenovirus, viral hepatitis and Toxoplasma gondi. In primary infections of adults with clinically atypical diseases, EBV-specific laboratory diagnosis may also be helpful.

•  McKesson Consult ® Mononucleosis Cassette Test for the whole blood test is classified as waived under CLIA ’88 regulations.

• Open or broken/damaged pouches may produce erroneous results due to kit instability from exposure to moisture and should be discarded.

Expected Values:

1. In patients with symptoms indicating IM, a positive heterophile antibody result is diagnostic and no further testing is necessary. During the acute phase of illness, IM-specific heterophile antibodies are detectable in 80-85% of IM cases. Humoral responses to primary infections appear to be quite rapid. Moderate to high levels of heterophile antibodies are seen during the first month of illness and decrease rapidly after week four.

2. Positive test results may persist for months or even years due to the presence of persistent IM heterophile antibodies. This may occur with or without any clinical symptoms or hematological evidence of IM. Conversely, a confirmed heterophile antibody test may indicate an occult infection.  In fact, detection of IM prior to onset of clinical symptoms have been reported.

3. Some patients remain persistently negative, even though there may exist hematological and clinical evidence of IM. In some of these patients, serological evidence for a diagnosis of cytomegalovirus infection, toxoplasmosis, or viral hepatitis, as well as others, have been found.

Interference: No significant interference from visibly hemolyzed, lipemic and icteric samples. Do not use grossly hemolyzed blood specimens.

Key Points: 

References:

  • Product insert, Consult Mononuclosis Tests Cassette, Distributed by McKesson Medical-Surgical Inc., Richmond, VA 23233 Rev.00 12/15 San  Diego, Inc