Evaluation of biological reference interval of 25 Hydroxy Vitamin D in West Bengal

The number of patients visiting pain clinic and being suggested for estimation of 25 hydroxy vitamin D(25OHD) have increased surprisingly. The 25OHD results being estimated by the laboratory have also shown values below the health reference range in majority number of cases. Such a large number of 25OHD deficient patient in adult population without any presentation of classical deficiency symptom except generalized pain and fatigue seems improbable and the author decided to evaluate the local health reference range. The manufacturer also suggests to evaluate the BRI in the laboratory in the inserts. The established Biological reference Interval (BRI)of 25 hydroxy Vitamin D(25OHD) which is popularly known as health reference range and BRI obtained from population based study by the kit manufacturer (Roche Diagnostics) were found out to be not in accordance. The local population results did not correlate with established BRI but nicely correlated with the population study result of the manufacturer.

Healthy volunteers, male and female were chosen. Selection of healthy population was as per CLSI (Clinical &Laboratory Standards Institute) instruction. Reference range has been established from non parametric distribution. Both male and female patient population were simultaneously evaluated to find out whether 25OHD was the sole attributor of the patient complaints or health reference range should be replaced by population based reference range. Patients are of same age group with the volunteers with no history of addiction and any other history of chronic disease or medication except they are from pain clinic came with the history of joint pain, body ache, fatigue. 25 OHD of both patient and healthy volunteer group was estimated in Cobas e 411 system by electro chemi luminescence immunoassay(ECLIA). The pain profile parameters were uric acid (UA), totalcalcium (Ca), C-Reactive protein(CRP) and rheumatoid arthritis factor(RF) were usual test requirements along with 25OHD. The parameters were tested for both patient and volunteer group. The tests were performed in Cobas Integra 400 plus. Number of male healthy volunteers was 120 and female 122 which satisfies the criteria of CLSI for reference range determination.

The BRI established by the laboratory is in accordance with the population study of Roche Diagnostics. The author mentions the evaluated reference range as “Laboratory Evaluated Reference range” in the test results.