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Dear Editor,
Cobalamin levels are frequently requested in geriatric practice. The focus is usually on detecting B12 deficiency, as shown by an extensive literature (1-4). In contrast, little is known about the meaning of high cobalamin levels (5). Previous data indicate that an elevated serum vitamin B12 level is a predictive factor for mortality in elderly patients with cancer (6). It therefore seems that elevated levels of serum cobalamin may be a sign of a serious, even life-limiting, illness. Diseases such as leukaemias, myeloproliferative disorders, hypereosinophilic syndrome, metastatic cancer - especially when involving the liver - are often accompanied by elevated cobalamin levels (7-13). Mechanisms of high vitamin B12 level may be explained by an upregulation of transcobalamin synthesis, increased release of cellular cobalamin, or decreased clearance of cobalamin from plasma (7). In the daily geriatric practice, (biochemical) predictors that help to estimate mean survival are of great interest by possibly preventing futile hospitalizations, over-diagnosis and subsequent over-treatment.
Our aim was to assess whether elevated serum vitamin B12 level could be a predictor of mortality in elderly inpatients aged over 65 years. During 3 months, we assessed vitamin B12 level in all 488 consecutive admissions (138 men, 350 women; average age: 84.7 years, ranging from 65 to 101 years) to the Geriatric Department of Geneva University Hospitals. Patients receiving cobalamin therapy were excluded from the study. Laboratory screening of vitamin B12 was routinely performed the day following admission, using the chemiluminescent immunoassay system technique (IMMULITE®2000 Vitamin B12, L2KVB6; Diagnostic Product Corporation, Los Angeles, USA,).
Two years after B12 measurement, the Geneva State population office registry was consulted to obtain patients' date of death. A logistic regression model with death as the dependant variable was used to perform a sensitivity analysis aiming at defining the best cobalamin cut off point. Survival curves were computed using the Kaplan-Meier method and compared using the log rank test. Cox proportional hazards models were used to estimate the influence of gender, age and the presence of cancer on the risk of mortality. Statistical analyses were performed using the Stata release 8.2 software package.
Median serum vitamin B12 level was 298 pmol/1 (interquartile range (IQR) 285) and 33.8% of the patients had high vitamin B12 level (≥ 400 pmol/1). The...