Laboratory studies in coagulation disorders.

It is important to go in a stepwise approach to diagnose spectrum of bleeding disorders, so that minimum tests are undertaken to make a definitive diagnosis and to avoid unnecessary tests and laboratory load. Depending on the abnormalities observed in the short screening, extended screening tests can be performed followed by specialized diagnostic tests. Bleeding time is prolonged in thrombocytopenia and platelet function disorders (PFD). If platelet count is normal, extended screening tests such as RVVT, PF3 availability and clot retraction can be performed. Russel viper venom directly activates FX, in presence of PF3, is an indicator of common pathway of coagulation. However, if there is deficiency of PF3 as obtained in PFD and APTT PT are normal, its prolongation indicates PFD. These can be tested invitro by performing RVVT with and without inosithin it is highly suggestive of underlying PFD. In such cases, diagnostic tests for PFD such as platelet aggregation with ADP, ADR, AA, Collagen and Ristocetin can be performed followed by electron microscopy if possible. Few of the interesting cases also have been discussed in the text.