Early identification of radiographic osteoarthritis of the hip using an active shape model to quantify changes in bone morphometric features: can hip shape tell us anything about the progression of osteoarthritis?

OBJECTIVE: Few methods exist to measure the progression of osteoarthritis (OA) or to identify people at high risk of developing OA. Striking radiographic changes include deformation of the femoral head and osteophyte growth, which are usually measured semiquantitatively following visual assessment. In this study, an active shape model (ASM) of the proximal femur was used to determine whether morphologic changes to the bone could be quantified and used as a marker of hip OA. METHODS: One hundred ten subjects who had no signs of radiographic hip OA at baseline (Kellgren/Lawrence [K/L] scores 0-1) were selected from the Rotterdam Study cohort of subjects ages > or = 55 years. To measure the progression of OA, subjects were followed up with radiographic assessment after 6 years. At the 6-year followup, 55 subjects had established OA (K/L score 3), and in 12 of these OA subjects, the progression of the disease required a total hip replacement (THR). Age- and sex-matched control subjects had a K/L score of 0 at followup. Using the ASM, subjects were assessed for shape changes in the femoral head and neck before, during, and after the development of radiographic OA. Scores of shape variance, or mode scores, were assigned for 10 modes of variation in each subject, and differences in mode scores were determined. RESULTS: During followup, significant changes in shape of the proximal femur occurred within the OA group from baseline to followup (P < 0.0001 for mode 1 and P = 0.002 for mode 6) but not within the control group. At baseline (all subjects having K/L scores 0-1), there were significant differences in mode 6 between the OA group and the control group (P = 0.020), and in modes 3 and 6 between the OA subjects who underwent THR and the remaining OA subjects (P = 0.012 and P = 0.019, respectively). CONCLUSION: Compared with traditional scoring methods, the ASM can be used more precisely to quantify the deforming effect of OA on the proximal femur and to identify, at an earlier stage of disease, those subjects at highest risk of developing radiographic OA or needing a THR. The ASM may therefore be useful as an imaging biomarker in the assessment of patients with hip OA.     

Evaluating novel cardiovascular risk factors: can we better predict heart attacks?

Myocardial infarction often occurs among persons without traditional risk factors, and it has been hypothesized that assessment of "novel" markers may help identify persons who are prone to premature atherothrombosis. However, when considering the clinical utility of screening for any new marker for cardiovascular disease, physicians should consider whether there is a standardized and reproducible assay for the marker of interest; whether there is a consistent series of prospective epidemiologic studies indicating that baseline elevations of the novel marker predict future risk; and whether assessment of the novel marker adds to the predictive value of other plasma-based risk factors, specifically, the ratio of total cholesterol to high-density lipoprotein cholesterol. In this article, these criteria are used to evaluate five promising markers of cardiovascular risk: lipoprotein(a), total plasma homocysteine, fibrinolytic capacity, fibrinogen, and high-sensitivity C-reactive protein. Background is also provided to assist physicians in deciding whether one or more of these novel markers deserve clinical consideration in general outpatient settings.     

Early identification of radiographic osteoarthritis of the hip using an active shape model to quantify changes in bone morphometric features: Can hip shape tell us anything about the progression of osteoarthritis?

Objective

Few methods exist to measure the progression of osteoarthritis (OA) or to identify people at high risk of developing OA. Striking radiographic changes include deformation of the femoral head and osteophyte growth, which are usually measured semiquantitatively following visual assessment. In this study, an active shape model (ASM) of the proximal femur was used to determine whether morphologic changes to the bone could be quantified and used as a marker of hip OA.

Methods

One hundred ten subjects who had no signs of radiographic hip OA at baseline (Kellgren/Lawrence [K/L] scores 0–1) were selected from the Rotterdam Study cohort of subjects ages ≥55 years. To measure the progression of OA, subjects were followed up with radiographic assessment after 6 years. At the 6‐year followup, 55 subjects had established OA (K/L score 3), and in 12 of these OA subjects, the progression of the disease required a total hip replacement (THR). Age‐ and sex‐matched control subjects had a K/L score of 0 at followup. Using the ASM, subjects were assessed for shape changes in the femoral head and neck before, during, and after the development of radiographic OA. Scores of shape variance, or mode scores, were assigned for 10 modes of variation in each subject, and differences in mode scores were determined.

Results

During followup, significant changes in shape of the proximal femur occurred within the OA group from baseline to followup (P < 0.0001 for mode 1 and P = 0.002 for mode 6) but not within the control group. At baseline (all subjects having K/L scores 0–1), there were significant differences in mode 6 between the OA group and the control group (P = 0.020), and in modes 3 and 6 between the OA subjects who underwent THR and the remaining OA subjects (P = 0.012 and P = 0.019, respectively).

Conclusion

Compared with traditional scoring methods, the ASM can be used more precisely to quantify the deforming effect of OA on the proximal femur and to identify, at an earlier stage of disease, those subjects at highest risk of developing radiographic OA or needing a THR. The ASM may therefore be useful as an imaging biomarker in the assessment of patients with hip OA.

     

Passive surveillance as an instrument to identify risk factors for fatal Rocky Mountain spotted fever: is there more to learn?

National surveillance for Rocky Mountain spotted fever (RMSF) dates from 1920; however, the collection of detailed epidemiologic, clinical, and laboratory data on RMSF by using case report forms began in 1970. Despite issues with compliance and changes in case definitions, surveillance data have permitted researchers to assess risk factors for fatal RMSF quantitatively. Factors consistently associated with increased risk of death include severity of disease, older age, lack of tick bite, absence of classic symptoms, delay in diagnosis and initiation of appropriate antibiotic treatment, and treatment with chloramphenicol only. In several studies, treatment with a tetracycline has been shown to be protective. The continuation of current passive surveillance activities may allow researchers to refine their estimates of risk but is unlikely to produce novel results. Modified surveillance activities could focus on evaluating the risk for fatal RMSF among special populations, monitoring appropriate antibiotic use, and assessing new diagnostic tests.