CLINICAL LAB SCIENEC

CHAPTER 16: IMMUNOLOGY AND SEROLOGY 411
slide for positive reactions. Other methods
are available that use automated systems
such as nephelometers. Nephelometers are
similar to spectrophotometers but measure a
phenomenon called precipitation rather than
agglutination. Some manual tests provide
for procedures that include a sophisticated
method called enzyme immunoassay.
A number of limitations are associated
with this procedure. As with other clinical
laboratory procedures, the results obtained
with the kits for determining the presence of
RF must be evaluated by the physician by correlating
the clinical picture of symptoms and
FIGURE 16-4 Rheumatoid factor latex agglutination kit.
Source: Delmar/Cengage Learning.
signs. Those specimens showing gross hemolysis, lipemia, and turbidity should not be
used, as these characteristics may indicate deterioration of the sample. The strength
of agglutination in the procedure does not indicate the severity of the disease state.
Weak reactions are possible with slightly elevated or markedly elevated antinuclear
antibody concentrations. The antinuclear antibody test is designed for diagnosis of
another autoimmune disease, systemic lupus erythematosus (SLE).
Reaction times of more than 2 minutes may cause erroneous results. The ASI
brand of a direct RF slide test is classified as moderately complex under CLIA ’88
regulations, indicating that it should be performed by laboratory professionals.
Equipment and Supplies
1. Gloves, disposable paper towels, and disinfectant or other cleaning solution
2. Report form
3. Procedure kit (contains reagent, controls, and diluents)
4. Stirrer pipettes (act as both pipetters and contain a spatula end for stirring).
5. Test tubes (10 75 mm, or 13 100 mm) for diluting specimens and test
tube rack
6. Serological pipettes
7. Volumetric pipette to deliver 0.25 mL
8. Mechanical rotator (optional) (The low speed for rotating the slide does not
always lend itself to the need for a mechanical rotator and for most kits the slide
can be rotated by hand.)
9. Electronic timing device or clock/watch with second hand
Procedure
1. Wash hands and don gloves.
2. Assemble necessary equipment and supplies.
3. Ensure that all reagents and specimens are at room temperature before use.
4. Exercise care to avoid contamination of reagents with each other or with the test
specimens. Reagents contain sodium azide. Do not pipette by mouth!
5. Gently but thoroughly shake the latex reagent before use.
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