CLINICAL LAB SCIENEC

412
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
6. Run the positive control and negative
control concurrently with each group
of specimens tested. Do not dilute the
controls before testing.
7. Using the stirrer pipettes, deliver one freefalling
drop onto a separate circle for each
unknown sample to be tested.
8. Place one drop each of the positive control
FIGURE 16-5 Illustration of typical reaction showing both positive and negative control into two additional
and negative reactions.
rings on the slide.
Source: Delmar/Cengage Learning.
9. Expel residual reagent in the dropper and
refill. Add one drop of well-shaken latex
reagent to each section containing sample
and controls.
10. Using the flat end of a new stirrer for each ring, mix samples and reagent thoroughly,
spreading mixture over entire area.
11. Rock slide evenly and gently by hand 8 to 10 times per minute for 2 minutes.
12. Observe each mixture immediately at the end of two minutes for agglutination
(Figure 16-5). Failure to do so may cause erroneous results.
13. Record results of controls and unknown specimens on the appropriate form.
14. Wash slides quickly following completion of the procedure as residue may dry on
the slide, then rinse with deionized water.
15. Discard all supplies used for the procedure in the appropriate containers.
A disinfectant should be used to clean the work surfaces and equipment should
be cleaned and restored to its former position. Gloves should be discarded
appropriately and the hands washed thoroughly in accordance with established
policies.
Reporting of Results
Typical test results (negative and positive) can be seen in Figure 16-5. Interpretation
of results is quite simple. Positive results show visible agglutination and negative
results appear uniformly turbid or milky. If either the undiluted or the diluted specimen
shows agglutination, the result should be reported as positive. When agglutination
occurs only in the diluted specimen, it indicates an excess of antibodies in the
undiluted specimen. This is called a prozone reaction and indicates that results
would increase with additional dilutions of the serum.
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