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4. Handle all specimens as potentially infectious.

5. Follow standard biosafety guidelines for handling and

disposal of potentially infective material.

Specimen Collection and Preparation

1. Blood samples collected with a suitable anticoagulant

such as EDTA or Heparin or Oxalate can also be used.

2. No prior preparation of the patient is required before

sample collection by approved techniques.

3. Fresh serum/plasma is preferable. Anticoagulated whole

blood can also be used as specimen. Serum/plasma may

be stored at 2 to 8°C up to 24 hours in case of delay in

testing. For long-term storage, freeze the specimen at

–20°C for 3 months or –70°C for longer periods. Whole

blood should be used immediately and should not be

frozen.

4. Repeated freezing and thawing of the specimen should

be avoided.

646 Concise Book of Medical Laboratory Technology: Methods and Interpretations 5. Do not use hemolyzed, clotted, contaminated,

viscous/turbid specimen.

6. Specimen containing precipitates or particulate matter

must be centrifuged and the clear supernatant only

used for testing.

7. For each sample, a new sample loop should be used.

Testing Procedure and Interpretation of Results

1. Bring the kit components to room temperature before

testing.

2. Open the pouch and retrieve the test device. Once

opened, the device must be used immediately.

3. Label the test device with the patient’s identity.

4. Add 10 µL of serum/plasma or whole blood with a

micropipette into the sample port “A”, OR using the

5 µL sample loop provided with the kit. Dip the loop

into the sample and then blot into the sample port

‘A’. Repeat this step twice for each sample. Ensure

that the loop does not retrieve clots or debris from

the sample.

5. Add 5 drops of sample running buffer to the reagent

port ‘B’.

6. At the end of 15 minutes read the results as follows.

Negative Test Result

Only one colored band appears in the control window ‘C’.

In addition to the band in control window ‘C’, another

red/purple band appears in the test window ‘T’ indicating

the presence of specific IgM antibodies to Leptospira.

¾ The test should be considered invalid if neither the

control band ‘C’ nor the test band ‘T’ appears. Repeat

the test with a new device.

Performance Characteristics

Leptocheck-WB was evaluated at the Royal Tropical

Institute, Amsterdam in parallel with other licensed tests

for the serodiagnosis of leptospirosis. The 47 sera evaluated

were from diverse serogroups of Leptospira.

Leptocheck-WB had a performance comparable to the

other tests.

Remarks

1. The intensity of the test line depends upon the stage of

the disease and the titres of the antibodies in the test

specimen.

2. As specific antibodies reach detectable levels about

one week after the onset of disease, a sample collected

very early may yield a negative test result.

3. If the test is negative and if leptospirosis is still

suspected, the test should be repeated with the second

sample collected at a later date in conjunction with

clinical reexamination.

4. In endemic areas, faint bands may appear occasionally

due to borderline IgM titres present as a result of

previous exposures.

5. It is recommended that the positive results obtained

must be reconfirmed using a confirmatory test such

as the MAT (microscopic agglutination test).

6. High titres of RF and heterophile antibodies may

interfere with the test; in such cases, the results must

be interpreted with caution.

7. The results must be correlated with clinical findings

to arrive at the diagnosis.

8. Do not use the test kit beyond expiration date.

Possible causes Solutions

1.  The flow properties of the nitrocellulose membrane are partially

affected leading to the movement of partially aggregated gold-sol

particles

Check the pouch for pinholes and also observe the desiccant for any

color change. The results of the test should be correlated with clinical

findings.

Troubleshooting

Problem: False positive results

Serology/Immunology 647

Possible causes Solutions

1. Hemolyzed blood samples were used for testing Do not use hemolyzed blood samples for testing

2. Reading taken after 15 minutes Read results exactly at 15 minutes

Possible causes Solutions

1. Whole blood samples having microclots or fibrin Ensure that the whole blood collected directly from fingerprick (without anticoagulant) should be free from microclots to avoid altered

flow and delayed reaction time

Problem: Faint Lines observed in control and test region

Problem: delayed results and altered flow

Problem: false negative results

Possible causes Solutions

1. Inadequate quantity of sample used for performing the test The exact number of drops of the sample as mentioned in the pack

insert should be dispensed for performing the test using the dropper

provided with the kit

2. The kit is exposed to very high temperatures leading to

deterioration of the antibodies coated on the device

Store at recommended temperature when not in use

3. Turbid or contaminated serum samples were used for testing Do not use turbid or contaminated serum samples for testing

4. Sample tested early after infection Specific antibodies reach detectable levels about one week after onset

of disease; hence,