title: The prevalence of recognized contributors to secondary osteoporosis in South East Asian men and post-menopausal women. Are Z score diagnostic thresholds useful predictors of their presence?
abstract: The prevalence of secondary contributors to osteoporosis in our population of SE Asian patients is high. Though various low thresholds Z score values have been proposed as suggestive of a high likelihood of secondary osteoporosis, they appear to have only limited discriminatory value in identifying a secondary cause.
  
  
  BACKGROUND
  Many patients with osteoporosis have significant secondary contributors towards their bone loss. The sensitivity and diagnostic utility of using Z score thresholds to screen for secondary osteoporosis have not yet been convincingly demonstrated nor has there been any previous attempt to estimate the prevalence of secondary osteoporosis in South East Asia. We aimed to study the prevalence of commonly recognized contributors and to determine the discriminatory ability of Z score thresholds in screening for them in Singaporean men and post-menopausal women with osteoporosis.
  
  
  METHODS
  Three hundred thirty-two consecutive patients seen at the osteoporosis clinic of the largest hospital in Singapore were evaluated. The frequencies of the different contributors were determined and sensitivities, specificities, and positive and negative predictive values (PPV and NPV) of pre-specified Z score cut-off values calculated.
  
  
  RESULTS
  Vitamin D deficiency was present in 18.5% of the patients, hyperthyroidism in 10.11%, primary hyperparathyroidism in 1%, secondary hyperparathyroidism in 6%, hypercalciuria in 21.63%, glucocorticoid use in 8.43%, and hypogonadism in 9.4% of males. A Z score value of <-1 had a sensitivity of 71.7 % and NPV of 66.2 % in identifying the presence of a secondary contributor in post-menopausal women. The sensitivity and NPV of a similar threshold in men was 59.1 and 40 %, respectively. ROC curves used to investigate various Z score diagnostic thresholds for sensitivity and specificity showed that they provided poor predictive value for the presence of secondary osteoporosis.
  
  
  CONCLUSIONS
  Secondary contributors are common in our patients with osteoporosis. Z score diagnostic thresholds have only limited value in discriminating between primary and secondary osteoporosis.
authors.affiliation: Department of Endocrinology, Osteoporosis and Bone Metabolism Unit, Singapore General Hospital, Outram Road, Singapore 169608, Singapore.
authors.forename: Chee Kwang
authors.initials: CK
authors.lastname: Yung
authors.forename: Stephanie
authors.initials: S
authors.lastname: Fook-Chong
authors.forename: Manju
authors.initials: M
authors.lastname: Chandran
mesh_terms: D000368:Aged; D001210:Asia, Southeastern / Q000453:epidemiology; D005260:Female; D006801:Humans; D053565:Hypercalciuria / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology; D006961:Hyperparathyroidism / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D017698:Postmenopause; D011237:Predictive Value of Tests; D015995:Prevalence; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012846:Singapore / Q000453:epidemiology; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D