A POPULATION STUDY OF THE SCREENING POTENTIAL OF ASSESSMENT OF TRABECULAR PATTERN OF THE FEMORAL-NECK (SINGH INDEX) - THE CHINGFORD STUDY

The trabecular pattern of the femoral neck (Singh index) has been used as a measure of osteopenia and fracture risk but the value of this me thod is controversial. This study assessed the usefulness of the Singh index (SI) by using dual energy X-ray absorptiometry (DXA) as the ''g old standard''. 659 Caucasian women (45-70 years) from an age-sex regi ster of a general practice had their femoral neck and lumbar spine bon e densities measured by DXA and had antero-poslerior hip X-rays perfor med which were then categorized into six osteopenia grades using the S I method. The intraobserver and interobserver reproducibility of this method was good (kappa = 0.64 and 0.61, respectively). The SI grades c orrelated significantly with body mass index (r = 0.35) and age (r = 0 .17) (p < 0.001). The mean femoral neck and lumbar spine bone densitie s were significantly higher with increasing SI grade even after adjust ment for age and body mass index (p < 0.001). The proportion of subjec ts below the fracture threshold (2 SD below mean peak bone mass) decre ased with increasing SI grade, ranging from 100% in SI grade 2 to 16.8 % in SI grade 6. There was, however, wide overlap of bone densities be tween the grades. Using the criteria ''osteoporosis less than or equal to SI grade 4'', the sensitivity and specificity of the SI method dia gnosing low bone mass was 35.1% and 90.0%, respectively. These data su ggest that the SI is a reproducible tool which may detect differences in bone mass between populations or subgroups within populations, alth ough caution should be used in classifying individual patients because of the wide variation in bone density. The method has a low sensitivi ty but a relatively high specificity in diagnosing low bone mass.