6. The RHELAX RF reagent is free from prozone effect

at RF levels between 10 IU/mL to 2300 IU/mL of RF

concentration.

7. The RHELAX RF reagent is sensitive to the presence of

IgM RF with heterogeneous specificity.

658 Concise Book of Medical Laboratory Technology: Methods and Interpretations Troubleshooting

Problem: False positive results

Possible causes Solutions

1. Plasma is used as a test specimen Only serum must be used for testing

2. Samples are stored for a long period Should a delay in testing occur, store samples at 2–8°C. Samples can

be stored for upto a week at 2–8°C

3. Markedly lipemic, hemolyzed and contaminated serum samples

could produre non-specific results

Avoid using lipemic, hemolyzed and contaminated serum samples for

testing

4. Drying of the reagent on the slide Do not read results beyond 2 minutes. The test should be carried out

directly under the fan

5. Presence of dust or debris on the glass slide used Dust or debris could be misinterpreted as agglutination therefore,

only clean and dry glass slides must be used for testing

6. Latex particles contaminated with positive control/positive

sample

Care must be taken to see that the latex reagent dropper tip does not

touch the sample or control taken on the slide during dispensing of

the reagent

7. Wrong dropper used for dispensing the sample Accessories provided with the kit only must be used for optimum

results

8. Increase in drop size, thereby leading to excess reagent dispensed. Excess reagent dispensed gives false positive results at borderline

concentrations. Ensure that exactly one drop of reagent is dispensed

onto the slide

9. Reagent dropper not held vertically while dispensing To ensure accurate dispensing of the reagent, hold the regent dropper

vertically while dispensing the reagent

10.Dried latex particles observed in the latex reagent:

•  During slide test with negative control

•  In the dropper of the vial (due to freezing of the latex reagent

during storage)

•  Improper dispensing of the entire reagent from dropper

Immediately after performing the test, transfer the contents of the

reagent dropper back into the reagent vial

Ensure that no reagent is left behind in the dropper. Close the cap

of the reagent vial properly and store it back at 2–8°C

Do not freeze the reagent vial

Problem: False negative results

Possible causes Solutions

1. The reagent may be damaged due to microbial contamination or

exposure of extreme temperatures

Performance of the reagents can be verified by using positive control/

known positive sample

2. Weak agglutination may be interpreted as a negative result Shake the latex reagent well before use to disperse the latex particles

uniformly and improve test readability

3. Samples stored for a long period of time are used as specimens Samples can be stored only for a week at 2–8°C

4. Hemolyzed samples may be used for testing Avoid using hemolyzed samples

5. If the conclusion of false negative result has been arrived by

comparison with another kit, this other kit could be giving a false

positive reaction

Run the test with a third kit to validate the results

6. Decrease in drop size, therby leading to less amount of reagent

dispensed

Less amount of reagent dispensed gives false negative results at

borderline concentrations. Ensure that exactly one drop of reagent is

dispensed onto the slide

7. The latex reagent might have been frozen The latex reagent should never be frozen as freezing leads to the dissociation of human IgG coated on the latex. The free IgG neutralizes

the RF present in the sample thereby leading to false negative results

Serology/Immunology 659

Problem: Positive control giving negative reaction

Possible causes Solutions

1. The positive control may have deteriorated due to contamination

or exposure to extreme temperatures

Check the performance of the latex reagent using known positive

samples. If the latex reagent is working then the positive control may

have deteriorated

Possible causes Solutions

1. Reagents not brought to room temperature before testing Bring the reagents to room temperature before carrying out the test

Problem: Delayed agglutination

SLIDE TEST FOR ANTI DEOXYRIBONUCLEOPROTEIN (RHELAX SLE)

(Courtesy: Tulip group of companies)

Summary

The presence of autoantibodies to nuclear proteins is a

common finding in systemic lupus erythematosus (SLE)

and other collagen diseases.