Diagnosing (severe) Osteoporosis by Hologic vs. Lunar Measurements: A Single-Center Retrospective Study

Abstract

Introduction: Although different dual-energy X-ray absorptiometry (DXA) scanners provide different bone mineral density (BMD) values, there is not a gold standard DXA scanner. T-score is used to facilitate the interpretation of BMD, and osteoporosis (OP) is diagnosed based on T-scores. In this retrospective study, we aimed to evaluate the BMD and T-score differences between Lunar Prodigy and Hologic Horizon DXA scanners.

Methodology: Data were collected for patients with previous BMD measurement on Lunar Prodigy and Hologic Horizon DXA scanners within one year in the same medical center.

Results: In a total of 55 patients, BMD values of femoral neck/total, and lumbar vertebrae were all lower at Hologic than Lunar (all p < 0.01). The mean T-score difference at the lumbar spine was 0.74 ± 0.42 (p < 0.001). Of the 49 patients diagnosed as OP (T-score ≤-2.5) with the Hologic, the diagnoses were changed for 25 individuals (51.0 %) with Lunar (p < 0.001). Herewith, although the diagnoses of OP did not change by the repeat technique in other 24 patients (49 %), 13 of them (26.5 %) were categorized as having "high fracture risk" instead of "very high fracture risk" group (i.e., T-score <-3.0). We observed moderate-to-good reliabilities (with an intraclass correlation coefficient [ICC] of 0.633-0.878 and 0.733-0.842 for BMD and T-scores, respectively) between measurements with the Lunar and Hologic scanners. Except for one measurement in L3, L4, L1-4 vertebrae, the Bland-Altman plot did not reveal any consistent bias between the measurements of the Lunar and Hologic scanners.

Conclusions: The consistency between different DXA scanners (especially for Hologic vs. Lunar) is important for proper management, especially in patients with low T-scores and OP.

Keywords: DXA; Fracture; Lumbar spine; T-score.