The BMD values of the participants registered in the KNHANES database and of the AFF patients in our hospital were measured at the LS (L1–L4), FN, and TF by DXA using the Hologic QDR4500A (Hologic Inc., Waltham MA, USA) and Lunar DPXMD densitometer (GE Healthcare, Madison WI, USA). The precision errors for BMD measurements of both instruments were 1.9% and 1.5% in the LS and 1.8%–2.5% and 1.3%–2.2% in the femoral regions. To calibrate the BMD values of the AFF patients (from Lunar) to the KNHANES data (from Hologic), a cross-calibration equation as per a previous study16) (link) was applied.
T-score was standardized using the reference value provided by the World Health Organization (WHO).13) (link) The T-score of FN was generated by comparing the FN BMD values of the subjects with reference FN BMD values of Caucasian women aged 20–29 years derived from the National Health and Nutrition Survey III.17 (link)18) (link) The T-score of LS was generated by comparing the LS BMD values of the subjects with reference LS BMD values of Caucasian women aged 20–29 years derived from Hologic.18 (link)19) (link)
Osteoporosis was diagnosed based on the definition provided by the WHO: the lowest T-score among the FN, TF, and LS should be –2.5 or less, provided the T-scores of the FN and TF were measured in the unfractured femur.