Determinants of Serum 25-Hydroxyvitamin D Concentrations and a Screening Test for Moderate-to-Severe Hypovitaminosis D in Chinese Patients Undergoing Total Joint Arthroplasty.

Background: Hypovitaminosis D is associated with adverse surgical outcomes. We quantified the environmental, demographic, and modifiable determinants of serum 25-hydroxyvitamin D (25-OHD) concentration and assessed the potential impact of a preoperative screening questionnaire for moderate-to-severe hypovitaminosis D (25-OHD <30 nmol/L).

Methods: In a retrospective cohort study of 227 Chinese patients (69 males and 158 females) undergoing 261 joint arthroplasty, we collected information on recent sun exposure, dietary vitamin D intake, vitamin D supplementation, and Western Ontario and McMaster Universities osteoarthritis index using a questionnaire and measured a fasting 25-OHD concentration using a liquid chromatography-tandem mass spectrometry before surgery.

Results: The multiple regression model on the determinants of 25-OHD concentration described 14% of the total variance, with the greatest relative contribution from ambient ultraviolet radiation (42%). A 4-item screening test for moderate-to-severe hypovitaminosis D had acceptable discrimination (area under receiver operating characteristic curve = 0.76, 95% CI, 0.65-0.87), good calibration (Hosmer-Lemeshow goodness-of-fit; P = .93). Decision curve analysis showed that the screening test can potentially reduce unnecessary 25-OHD testing by 390 per 1000 patients at a threshold probability of 10%.

Conclusion: The screening test appears moderately useful in avoiding a substantial number of unnecessary 25-OHD testing in a setting where the prevalence of moderate-to-severe hypovitaminosis D is less than 10%.