Warfarin demonstrates a wide interindividual variability in response that is mediated partly by variants in cytochrome P450 2C9 (CYP2C9) and vitamin K 2,3-epoxide reductase complex subunit 1 (VKORC1). It is not known whether variants in calumenin (CALU) (vitamin K reductase regulator) have an influence on warfarin dose requirements. We resequenced CALU regions in a discovery cohort of dose outliers: patients with high (>90th percentile, n = 55) or low (<10th percentile, n = 53) warfarin dose requirements (after accounting for known genetic and nongenetic variables). One CALU variant, rs339097, was associated with high doses (P = 0.01). We validated this variant as a predictor of higher warfarin doses in two replication cohorts: (i) 496 patients of mixed ethnicity and (ii) 194 African-American patients. The G allele of rs339097 (the allele frequency was 0.14 in African Americans and 0.002 in Caucasians) was associated with the requirement for a 14.5% (SD ± 7%) higher therapeutic dose (P = 0.03) in the first replication cohort and a higher-than-predicted dose in the second replication cohort (allele frequency 0.14, one-sided P = 0.03). CALU rs339097 A>G is associated with higher warfarin dose requirements, independent of known genetic and nongenetic predictors of warfarin dose in African Americans. Clinical Pharmacology & Therapeutics (2010) 87 4, 445–451. doi:10.1038/clpt.2009.291
Performing a manual body fluid count is a tedious, time-consuming, and frequently imprecise process for any clinical laboratory. The ability to perform many of these counts with an automated hematology analyzer has the real potential of making a major impact on laboratory precision and productivity. The manual chamber count is fraught with many variables and is often very technologist/technique dependent, often leading to inaccuracies in test results. Our laboratory undertook a series of studies designed to evaluate the capability of the Coulter LH 750 hematology analyzer to supplement our current manual method in the performance of body fluid analysis. First, we established the performance of our current manual counting method, the gold standard against which LH 750 performance would be judged. We looked at the precision of manual cell counting by having 4 technologists perform manual counts on each of 35 spinal, synovial, peritoneal, and other fluids with white blood cell (WBC) and/or red blood cell (RBC) counts of greater than 0.3 x 10(9) /L and 0.03 x 10(12) /L, respectively. Our results support earlier reports that the variability in counts among technologists using the manual chamber cell count methods is often very significant. After each sample was manually counted, it was analyzed on the Coulter LH 750, and the results were compared with those of our current manual method. Results showed good correlation between the manual and LH 750 methods. Next, we conducted a series of separate tests to evaluate the stability of different cellular elements (WBCs and RBCs) in each of these body fluid types. The study consisted of 2 sets of 4--3-mL samples of each fluid type--which were analyzed on the LH 750 immediately on receipt and after 1 hour, 4 hours, 8 hours, 16 hours, and 24 hours. The findings suggested varying degrees of stability that were dependent on fluid type and initial cell concentration. Finally, we looked at whether it is necessary to perform background counts before analyzing each body fluid sample and the impact of automating body fluid counts on our workload.
