Minimal error in self-report of having had DXA, but self-report of its results was poor.

Objective: To examine the validity of both self-report of having had dual-energy x-ray absorptiometry (DXA) and self-reported DXA test results.

Methods: Participants were recruited in 2003 and 2004 from a population-based study of women aged 65-90 years examining osteoporosis management in Ontario, Canada (N=871). Women reporting having had a DXA were eligible and asked to report the results of their most recent test. Participant responses were compared against DXA reports obtained from physicians.

Results: We obtained 413 (81%) physician records among the 510 women who reported having had a DXA test. Of these, the positive predictive value for self-report of having had a DXA was 93%. The weighted kappa statistic for the agreement between self-report and actual DXA results was 0.42 (95% confidence interval=0.34-0.49). Although 84% of those with normal bone reported this, only 29% of those with osteopenia and 62% with osteoporosis reported their results correctly. Self-report of a clinical diagnosis of osteoporosis was better among those with a low trauma fracture, yet underestimated osteoporosis prevalence by 24%.

Conclusion: There is minimal measurement error in self-report of having had a DXA test. Self-report of DXA results will underestimate osteoporosis prevalence and is not a good proxy for clinical diagnosis.