A simple spectrophotometric method for the quantification of residual haemoglobin in platelet concentrates

Background and Objectives High levels of residual haemoglobin (Hb 0.1 g/l) are known to decrease the efficiency of pathogen-inactivation systems. We evaluated three separate methods to quantify Hb in platelet concentrates (PC). Materials and Methods Nine PC prepared in platelet additive solution (PASIII) (median platelet yield of 283 x 10(9)/unit, range 46-353) were spiked to known Hb concentrations with whole blood and the samples were measured by using each of three methods: the 3,3',5,5'-tetramethylbenzidine (TMB) oxidation method (Sigma Diagnostics, 527-A); the Harboe spectrophotometric method; and the HemoCue plasma low-Hb photometer (PLHP). Results The TMB and Harboe methods showed linear results compared to expected Hb (r(2) greater than or equal to 0.981, P < 0.001) over the range tested (0.09-0.28 g/l) when the samples were haemolysed. The TMB method underestimated by an average of 6%, at and around 0.1 g/l Hb, compared to a 4% overestimation by the Harboe method and a threefold overestimation by the PLHP. The Harboe intra-assay coefficient of variation was less than or equal to 1.85% across all concentrations, which contrasted with 30% at and around 0.1 g/l for the TMB method. Conclusions The Harboe spectrophotometric method is convenient, safe, accurate and reproducible, and outperforms the TMB and PLHP methods for quantification of residual Hb in PC.