Validation of a Major and Clinically Relevant Nonmajor Bleeding Phenotyping Algorithm on Electronic Health Records.

PURPOSE: Bleeding is an important health outcome of interest in epidemiological studies. We aimed to develop and validate rule-based algorithms to identify (1) major bleeding and (2) all clinically relevant bleeding (CRB) (composite of major and all clinically relevant nonmajor bleeding) within real-world electronic healthcare data. METHODS: We took a random sample (n = 1630) of inpatient admissions to Singapore public healthcare institutions in 2019 and 2020, stratifying by hospital and year. We included patients of all age groups, sex, and ethnicities. Presence of major bleeding and CRB were ascertained by two annotators through chart review. A total of 630 and 1000 records were used for algorithm development and validation, respectively. We formulated two algorithms: sensitivity- and positive predictive value (PPV)-optimized algorithms. A combination of hemoglobin test patterns and diagnosis codes were used in the final algorithms. RESULTS: During validation, diagnosis codes alone yielded low sensitivities for major bleeding (0.16) and CRB (0.24), although specificities and PPV were high (>0.97). For major bleeding, the sensitivity-optimized algorithm had much higher sensitivity and negative predictive values (NPVs) (sensitivity = 0.94, NPV = 1.00), however false positive rates were also relatively high (specificity = 0.90, PPV = 0.34). PPV-optimized algorithm had improved specificity and PPV (specificity = 0.96, PPV = 0.52), with little reduction in sensitivity and NPV (sensitivity = 0.88, NPV = 0.99). For CRB events, our algorithms had lower sensitivities (0.50-0.56). CONCLUSIONS: The use of diagnosis codes alone misses many genuine major bleeding events. We have developed major bleeding algorithms with high sensitivities, which can ascertain events within populations of interest.

Tailoring of recommendations to reduce serious cutaneous adverse drug reactions: a pharmacogenomics approach.

The Health Sciences Authority launched a pharmacogenetics initiative in 2008 to facilitate evaluation of pharmacogenetics associations pertinent for Chinese, Malays and Indians in Singapore. The aim was to reduce the incidence and unpredictability of serious adverse drug reactions, with a focus on serious skin adverse drug reactions. This paper describes the gathering of evidence and weighing of factors that led to different genotyping recommendations for HLA-B*15:02 with carbamazepine and HLA-B*58:01 with allopurinol, despite both having strong genetic associations. Translation of pharmacogenomics at a national level requires careful deliberation of the prevalence of at-risk allele, strength of genetic associations, positive predictive value, cost-effectiveness and availability of alternative therapies. Our experience provides a perspective on translating genomic discoveries in advancing drug safety.

Novel CYP2C9 genetic variants in Asian subjects and their influence on maintenance warfarin dose.

BACKGROUND: Commonly occurring genetic variants in CYP2C9 are known to reduce catalytic activity and are associated with enhanced patient sensitivity to warfarin. Interethnic differences in warfarin dose requirement have been described in the Asian population, and we postulate that this could be related to genetic variants of CYP2C9 that are unique to ethnic groups. METHODS: We prospectively genotyped 125 patients who were receiving a stable daily warfarin dose to maintain international normalized ratio values between 2 and 3 through comprehensive sequencing of the promoter and coding regions of the CYP2C9 gene. RESULTS: The mean weight-adjusted warfarin maintenance dose was significantly lower for Malay and Chinese subjects than Indian subjects ( P <.001 and.014, respectively). Warfarin dose negatively correlated with age (r = -0.4, P <.001) but not with sex. Multiple variants were detected in the promoter, exonic, intronic, and 3'-untranslated regions of CYP2C9, of which 16 were novel, including 7 nonsynonymous exonic variants ( 208G>C, 374G>A, 485C>A, 895A>G, 1144C>T, 1190A>C, and 1362G>C ). CYP2C9*3, but not CYP2C9*2, was found in Chinese and Malay patients, and carriers of the CYP2C9*3 variant in Chinese ( P <.01) and Indian ( P <.01) patients, but not Malay patients ( P =.77), required less warfarin. The influence of the novel exonic variants on warfarin dose requirement was unclear, because they were rare, but the lower warfarin dose requirement for Chinese and Malay patients existed despite omission of individuals with any coding region variants from analysis. CONCLUSIONS: Interethnic differences in warfarin dosing in Asian subjects may result from other genetic, dietary, or environmental influences; however, these novel variants in the gene warrant further characterization through functional studies.