PCR-based determination of platelet mRNA-GPIIIa. PCR-based quantitation of β-actin and GPIIIa mRNAs in platelets from the proband, heterozygous relatives, and normal individuals was performed using the instrumentation and the fluorogenic probes of the Perkin-Elmer Cetus LS-50B TaqMan System as described in Materials and Methods. R and Q denote the fluorescence of the reporter and the quencher dyes, respectively. Values were corrected for internal quenching and expressed as GPIIIa/β-actin fluorescence ratios.