Development and validation of an eight-item calcium screener to assess daily calcium intake of patients with osteoporosis in clinical practice

Objective To validate a short food frequency questionnaire (screener) estimating daily average calcium intake from dietary sources to guide calcium supplementation of patients with osteoporosis in clinical practice. Methods An eight-item calcium screener was developed based on existing literature, food consumption data and expert opinion. Convergent validity was determined by comparison with 3-day food records using mean difference, Spearman’s correlation coefficients (SCC) and Bland-Altman analysis. Test-retest reliability was assessed by SCC and intraclass correlation coefficients (ICC). We calculated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) to identify patients requiring calcium supplementation (