Reliability of the assessment of disc degeneration on the lateral DXA scans.

Abstract

Given the prevalence and costs induced by osteoarthritis (OA), it is necessary to find a cheap and safe technique to evaluate it reliably. To assess the value of the lateral dual energy X-ray absorptiometry (DXA) spine scans for the diagnosis of disc degeneration. Seventy-seven individuals aged 18 and over, with or without disc degeneration, had both lateral thoracolumbar spine radiographs and DXA spine scans (≤6months between both exams). Disc degeneration was assessed using the Lane score. The images of 20 randomly selected individuals were assessed by two readers. Almost 13% of the thoracic levels were not assessable on the DXA scans. For the identification of the intervertebral levels on the DXA scans as interpretable or not, the intra-reader agreement was good (κ=0.81) and the inter-reader agreement was fair (κ=0.27-0.36). For the diagnostic criteria (osteophytes, disc space narrowing, osteosclerosis, overall grade), the intra-reader agreement was excellent for the radiographs (κ=0.89-0.92), good for the DXA scans (κ=0.64-0.83) and fair to moderate for the between-method comparison (κ=0.25-0.44). The inter-reader agreement was moderate to good for the radiographs (κ=0.49-0.66) and fair to good for the DXA scans (κ=0.32-0.74). In the per patient analysis (the most severe grade), the intra-reader agreement was excellent for the radiographs (κ=0.85-0.94), moderate to excellent for the DXA scans (κ=0.53-0.85) and poor to good for the between-methods comparison (κ=0.17-0.63). Our results do not support the use of DXA scans for the assessment of thoracolumbar disc degeneration.