"25-Hydroxyvitamin D" Assay now available in the Clinical Chemistry Laboratory

Effective Monday, January 9, 2012, the University of Iowa Hospitals and Clinics (UIHC) core clinical chemistry laboratory will start performing the test "VITAMIN D, 25-HYDROXY" (Epic # LAB535). The method will be an FDA-approved assay from Abbott Diagnostics. This test is currently sent-out to ARUP Laboratories. The sample requirements will remain as a single plasma separator tube. The test will be run 24 hours a day, 365 days a year with an expected turnaround time within 2 hours of receipt with the laboratory.

In correlation studies, 25-hydroxyvitamin D values between the Abbott method and the send-out test correlated very closely. Therefore, little difference in 25-hydroxyvitamin D plasma concentration should be seen for patients who have been tested in the past. The lower limit of the assay is 4 ng/mL, which is the same as the send-out test. The reference range and comment appended to results will be as follows:

Reference range for Epic in terms of flagging normal versus abnormal: 20-80 ng/mL

The following comment will be appended to all results:
Deficiency: Less than 20 ng/mL
Borderline: 20-29 ng/mL
Optimum level: 30-80 ng/mL
Possible toxicity: > 150 ng/mL

Institute of Medicine (IOM) and World Health Organization (WHO) guidelines designate 25-hydroxyvitamin D plasma concentrations below 20 ng/mL as deficient. Optimal 25-hydroxyvitamin D concentrations greater than 20 ng/mL may be considered for specific disease conditions. 25-Hydroxyvitamin D concentrations should be interpreted in context of clinical history and physical examination along with other laboratory studies, if indicated.

Questions should be directed to Matthew Krasowski, MD, PhD, medical director of the Clinical Chemistry Laboratory (384-9380, matthew-krasowski@uiowa.edu).