Isolated thrombocytopenia: should we routinely screen for antiphospholipid antibodies?

Antiphospholipid (aPL) antibodies are thought to be present in at least 25% of immune thrombocytopenia patients. Conversely, more than 25% of patients with aPL antibody syndrome (APLAS) present with thrombocytopenia.

To identify the rate of a PL antibody positivity in patients with isolated thrombocytopenia and correlate this finding with the occurrence ofthromboembolic (TE) events or equivalents.

By performing prospective andretrospective analysis of a series of 64 consecutive patients with moderate persistent thrombocytopenia, we established the serologic evidence of APLAS and performed the existing clinico-laboratory correlations. The presence of aPL antibodies in patients with thromocytopenia was tested for statistical significance using chi2 test of independence for categorical variables (one degree of freedom, 95% confidence) as well as Fisher's exact test for small numbers of observations.

We detected the presence of aPL antibodies in nine of 64 (14%) of patients with isolated thrombocytopenia and four of nine APLAS patients (approximately 44%) also tested positive for antiplatelet antibodies. Five of nine APLAS patients (approximately 56%) had a consistently increased mean platelet volume (MPV). Although the numbers are small, the values proved statistically significant. Two of nine APLAS patients (approximately 22%) developed TE events or equivalents, and two patients were subsequently diagnosed with systemic lupus erythematosus.

We believe that patients with isolated thrombocytopenia should be tested for the presence of aPL antibodies, as our findings have shown a correlation between the presence of aPL antibodies and occurrence of TE events. Identification of an APLAS subset in this context appears justified in terms of early institution of antiplatelet therapy, especially in patients with additional cardiovascular risk factors.