Surgery Alters Parameters of Vitamin D Status and Other Laboratory Results of Relevance to Fracture Liaison Services

Abstract

Background: Fracture liaison services (FLS) are advocated internationally to improve osteoporosis care following fragility fracture. As secondary causes of osteoporosis are common, FLS programs often perform laboratory testing in the immediate post-fracture interval. We hypothesized that laboratory tests, including indices of vitamin D status, obtained shortly after surgery may not accurately ascertain an individual's baseline status. If true, such alterations may confound subsequent fracture prevention efforts. Methods: Forty adults having elective primary total hip arthroplasty were studied as surrogates for hip fracture patients. Blood and urine was obtained two weeks before surgery, before anesthetic induction, on post-operative day one and six weeks after surgery. Serum total and free 25(OH)D, vitamin D binding protein (DBP), calcium, creatinine, albumin (Alb), alkaline phosphatase (ALP), plasma hemoglobin (Hgb) and urinary DBP/creatinine ratio (UDBP/Cr) were measured. Results: Twenty-eight women and 12 men (mean age 65.7 [8.7] years) had regional anesthesia with intraoperative sedation (n = 34), or general anesthesia (n = 6). Laboratory results were stable from two weeks before to the day of surgery. On the first day after surgery serum total 25(OH)D, DBP, calcium, creatinine,ALP, and Alb declined by 8-22% (p < 0.0001); free 25(OH)D and Hgb declined by 8% and 15% (p < 0.01) respectively; and UDBP/Cr increased by 32% (p < 0.01). Using a 25(OH)D < 30 ng/mL threshold, the prevalence of vitamin D inadequacy increased from 38% before surgery, to 68% the day after (p < 0.001). All laboratory values returned to baseline at 6 weeks after surgery. Conclusions: Laboratory values are altered immediately following elective total hip arthroplasty. Testing at that time does not accurately ascertain baseline status, and may lead to elevated estimates of vitamin D inadequacy, incorrect interventions and misallocation of health care resources. Laboratory results obtained in the immediate post fracture interval should be interpreted with caution in secondary fracture prevention management.