Screening of Osteoporosis in Menopausal Women using OSTA Index and KKOS Scoring System

Abstract

Screening of Osteoporosis in Menopausal Women using OSTA Index and KKOS Scoring System

Budsaba Wiriyasirivaj MD, MSc (Clinical epidemiology, LSHTM, UK)

Department of Obstetrics and Gynecology, BMA Medical College and Vajira Hospital

Objective: To determine diagnostic performance of the Osteoporosis Self-Assessment Tool for Asians (OSTA) index, and Khon Kaen Osteoporosis Study (KKOS) scoring system in identifying osteoporosis in menopausal women.

Study design: Descriptive study (diagnostic test).

Subjects: Six hundred and seventy menopausal women attending menopause clinic at BMA Medical College and Vajira Hospital between December 2004 and January 2008.

Methods: The data was retrospectively collected from the medical records of women who had lumbar and femoral neck bone mass density (BMD) measurement by dual energy X-ray absorptiometry (DEXA). Data on age and body weight were collected and calculated for OSTA index and KKOS scoring system. Diagnostic performance of each index comparing with standard DEXA were determined.

Main outcome measures: Sensitivity, specificity, positive predictive value, negative predictive value, and 95% confidence interval (95% CI).

Results: The mean age of the subjects was 54.1 + 6.3 years. Prevalence of osteoporosis (T-score £ -2.5) at lumbar spine and femoral neck were 14.0% and 3.4%, respectively. OSTA index at cutoff £-1 had a sensitivity and specificity of 54.3% (95% CI, 50.5-58.0) and 84.0% (95% CI, 81.3-86.8) respectively for lumbar spine and 65.2% (95% CI, 61.6-68.8) and 80.2% (95% CI, 77.2-83.2) respectively for femoral neck. KKOS scoring system at cutoff £ -1 had a sensitivity and specificity of 54.3% (95% CI, 50.5-58.0) and 80.4% (95% CI, 77.4-83.4) respectively for lumbar spine and 60.9% (95% CI, 57.2-64.6) and 76.8% (95% CI, 73.6-80.0) respectively for femoral neck. In this setting, OSTA index at cutoff £ 0 is more appropriate for osteoporosis screening with the sensitivity and specificity of 79.8% (95% CI, 76.8-82.8) and 64.4% (95% CI 60.8-68.0) respectively for lumbar spine and 82.6% (95% CI 79.7-85.5) and 59.7% (95% CI 55.9-63.4) respectively for femoral neck. Using three categories according to probability of having osteoporosis, BMD measurements can be postponed in the category at lowest risk (OSTA index > 0) and in the category at highest risk which treatment should be recommended (OSTA index > -3). BMD measurements are only necessary for those with index -3 to 0. This application can reduce unnecessary BMD measurements by 61.6%.

Conclusion: OSTA index is more convenient and effective than KKOS scoring system for identifying either lumbar spine or femoral neck osteoporosis in Thai postmenopausal women. Individuals with OSTA index of -3 to 0 should be targeted for BMD measurement by DEXA.

Keywords: menopause, screening, OSTA index, KKOS scoring system, osteoporosis

Vajira Med J 2010 ; 54 : 135-146