Platelet antibody detection in pediatric immune thrombocytopenic purpura: evaluation of three screening methods.

BACKGROUND AND OBJECTIVES

Immune thrombocytopenic purpura (ITP) is a common hematologic disorder, two forms of which occur in children. The detection of circulating platelet antibodies is helpful in diagnosis.

MATERIALS AND METHODS

We evaluated three different immunological methods for detecting platelet antibodies in the serum of children with ITP. These were: a solid-phase red-cell adherence test (SPRCA), an enzyme immunoassay (EIA), and an immunofluorescence test (PSIF).

RESULTS

The sensitivity of the methods in detecting IgG antibodies ranged from 28.1 (EIA) to 39.4% (SPRCA). We also looked for IgM antibodies by PSIF, thus raising the sensitivity of this test from 32.0 to 40.0%. A combination of two tests (SPRCA and EIA) allowed us to detect 61.8% positive samples. By doing all three tests, we obtained 71.3% positive samples. Finally, we reached 73.5% by adding PSIF for IgM. We found a higher frequency of circulating antibodies in both acute and chronic ITP at onset than in clinical remission. There were a few positive sera in chronic ITP, but not in the acute form in remission.

CONCLUSION

The individual tests each have a relatively low sensitivity, but the combination of all three increases the diagnostic effectiveness. The finding of platelet antibodies during remission may predict evolution toward a systemic autoimmune state.