Packed cell volume (PCV) was measured using the microhaematocrit method [15] . Briefly, Blood was obtained in capillary tubes. Tubes were centrifuged at 12,000 g for 5 minutes. The percentage cell volume compared to the whole tube volume was calculated (i.e. PCV). Mean (6 standard deviation, sd), minimum and maximum PCV for each clinical group are tabulated in Table 1 . For discovery and validation cohort, these data were compared using a one-way multiple ANOVA test (p,0.05).