[Pseudothrombocytopenia: clinical comment on 37 cases]

Pseudothrombocytopenia (PTCP) is characterized by in vitro EDTA-, pH-, temperature- and time-dependent clumping which gives rise to spurious piastrinopenia at platelet count in automatized analyzers. It is caused by serum immunoglobulins recognizing some cryptoantigens on the platelet surface membrane. Aim of this study was to evaluate the prevalence of PTCP in a series of patients and its clinical significance.

From all the inpatients, in Internal Medicine Division, during 29 months, we have considered as PTCP the thrombocytopenias persistent in EDTA and contemporaneously, missing with ACD at the automatized counter, after microscopic examination. Then we estimated: PTCP rate in regard to all patients, sex, age and morbid associations both in PTCP group and in all patients. These frequences were compared with the chi-square test.

37 cases of PTCP are observed from a cohort of 2922 inpatients (1.26%): 23 were males, 17 females; median age was 73.7+/-11.2. The frequency of the following associations was significantly higher in the PTCP group: solid tumors in 9/37 (24.3%), myelo- and lymphoproliferative syndromes in 7/37 (18.9%), autoimmune disease in 4/37 (10.8%).

This study suggests that PTCP is one of the more frequent thrombocytopenias: it is important to identify it, to avoid clinical and therapeutic mistakes. Moreover PTCP, in our study, is often correlated with important diseases. We can conclude that in hospitalized old patients, PTCP could represent a signal to search more severe illnesses.