THU422 Laboratory Evaluation For Etiologies Of Secondary Osteoporosis
Authors: Shah Nandi , Galitzer Hayley , Sellmeyer Deborah 
Published: October 2023

Abstract
Disclosure: N. Shah: None. H. Galitzer: None. D. Sellmeyer: None.
Data on the prevalence of laboratory abnormalities in individuals with osteoporosis is limited. The purpose of this study was to quantify the frequency of test results indicative of secondary osteoporosis in patients referred for skeletal fragility. A retrospective chart review was conducted on 653 consecutive patients referred for low bone density or fracture at Stanford Medical Center from October 2018 to December 2021. Patients were asked to complete a standardized set of laboratory tests including comprehensive metabolic panel, 25-hydroxyvitamin D (25OHD), parathyroid hormone (PTH), thyroid testing, complete blood count, phosphorus, celiac screening, and 24 hour urine calcium. Demographics, bone density, and laboratory results were extracted from the medical record; statistical analysis was performed using STATA. Subjects were 65 +/- 14 (mean+SD) years old. The majority were White (59%) or Asian (24%). Most (81%) were postmenopausal women, 10% were men &gt;50 years old, 9% were men under 50 and premenopausal women. Of men over 50/postmenopausal women, 32% had osteopenia and 67% had osteoporosis. Among premenopausal women/men under age 50, 67% had Z-scores of −2 or less. Over 99% of serologic testing was completed; however urine calcium testing was completed in 46% of subjects. Overall, 66% of subjects had at least one lab abnormality. The most common abnormalities were of PTH and 25OHD with 20% of each test showing abnormal results. Anemia was present in 16% of subjects, alkaline phosphatase and TSH each were abnormal in approximately 11% of subjects; serum phosphorus and calcium each were abnormal in 5% and celiac testing was positive in 1.2% of subjects. Of 299 subjects who completed urine collections, 27% had hypocalciuria (&lt;100 mg), 24% had hypercalciuria (&gt;250 mg). There was no difference in the prevalence of laboratory abnormalities among individuals with Z-scores &lt;=−2, p=0.14. CKD stage 3 or lower was present in 15% of subjects; this was not counted in the overall rates of lab abnormalities as it was anticipated this was known. The prevalence of any lab abnormality was higher (77% vs 64%) among subjects with eGFR&lt;60, p=0.01. PTH was significantly higher in individuals with 25 OH vitamin D levels &lt;30, p=0.006. This study reveals a high prevalence of laboratory abnormalities while screening for secondary osteoporosis. While urine collection can be cumbersome, the high prevalence (52%) of abnormal results demonstrates the importance of this test. The rate of celiac disease is low, however, these patients were asymptomatic other than low bone density and otherwise would be undiagnosed. Low Z-score did not predict lab abnormalities. Current guidelines do not provide consensus on laboratory testing for secondary etiologies of osteoporosis due to the paucity of data. This study highlights the importance of screening patients with metabolic bone disease to identify secondary contributors.
Presentation: Thursday, June 15, 2023