Platelet abnormalities in patients with cystic fibrosis and obligate heterozygotes.

Following our previous report that thrombocytosis and platelet hyperaggregability (as tested in platelet rich plasma) occur in patients with cystic fibrosis (CF), we have now examined whether this thrombocytosis is related to leukocytosis, and whether platelet hyperaggregability can be documented in whole blood using impedance aggregometry. Our observations show that platelet counts are related to white cell counts (r = 0.34; p = 0.001) and that therefore thrombocytosis may be part of a secondary response to bronchopulmonary infection, which is characteristic of these patients. Platelet counts were, however, not related to serum iron concentration despite the finding of varying degrees of iron deficiency in approximately 50% of patients with cystic fibrosis. Whole blood aggregometry demonstrated platelet hyperaggregability in patients with cystic fibrosis independently of platelet counts. Platelet aggregation (in platelet rich plasma and in whole blood) was normal in obligate heterozygotes, thus suggesting that platelet hyperaggregability in CF is not a consequence of abnormal genetic information.