Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1195 page)

   Syphilis

   TB

   Waldenström macroglobulinemia

   Limitations

   RF is not a finding isolated to RA and may be present in a number of connective tissue and inflammatory diseases, including infectious mononucleosis, SLE, scleroderma, and hepatitis.

   Older patients may have higher values.

   Recent blood transfusion, multiple vaccinations or transfusions, or an inadequately activated complement may affect results.

   Serum with cryoglobulin or high lipid levels may cause false-positive test results.

ROSETTE TEST
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   Definition

   The rosette test detects D-positive red cells in the blood of a D-negative mother, whose fetus or recently delivered baby is D positive.

   When anti-D reagent is added to the mother’s blood, fetal D-positive red cells become coated with anti-D on incubation and exhibit mixed-field agglutination when antiglobulin (see p. 884) reagent is added. Because the mixed-field agglutination may be difficult to detect, D-positive RBCs are added to the mixture to demonstrate rosettes of several cells clustered against antibodycoated D-positive cells.

   
Normal value:
Absence of rosettes is considered negative for major fetomaternal hemorrhage in an Rh-negative mother with an Rh-positive fetus.

   Use