ABSTRACT
BACKGROUND: In view of the importance of the diagnosis of rheumatoid arthritis, a novel diagnostic method based on spectroscopic pattern recognition in combination with laboratory parameters such as the rheumatoid factor is described in the paper. Results of a diagnostic study of rheumatoid arthritis employing this method are presented. METHOD: The method uses classification of infrared (IR) spectra of serum samples by means of discriminant analysis. The spectroscopic pattern yielding the highest discriminatory power is found through a complex optimization procedure. In the study, IR spectra of 384 serum samples have been analyzed in this fashion with the objective of differentiating between rheumatoid arthritis and healthy subjects. In addition, the method integrates results from the classification with levels of the rheumatoid factor in the sample by optimized classifier weighting, in order to enhance classification accuracy, i.e. sensitivity and specificity. RESULTS: In independent validation, sensitivity and specificity of 84% and 88%, respectively, have been obtained purely on the basis of spectra classification employing a classifier designed specifically to provide robustness. Sensitivity and specificity are improved by 1% and 6%, respectively, upon inclusion of rheumatoid factor levels. Results for less robust methods are also presented and compared to the above numbers. CONCLUSION: The discrimination between RA and healthy by means of the pattern recognition approach presented here is feasible for IR spectra of serum samples. The method is sufficiently robust to be used in a clinical setting. A particular advantage of the method is its potential use in RA diagnosis at early stages of the disease.
Subject(s)
Arthritis, Rheumatoid/blood , Arthritis, Rheumatoid/diagnosis , Rheumatoid Factor/blood , Adolescent , Data Display , Discriminant Analysis , Feasibility Studies , Female , Humans , Male , Middle Aged , Pattern Recognition, Automated , ROC Curve , Reference Values , Sensitivity and Specificity , Spectrophotometry, Infrared/instrumentationABSTRACT
We evaluated the AxSYM troponin I (cTnI) immunoassay for assisting in the detection of acute myocardial infarction (AMI). At four sites, the total imprecision (CV) over 20 days was 6.3-10.2%. The minimum detectable concentration was 0.14 +/- 0.05 microgram/L. Comparison of cTnI measurements between the AxSYM and Stratus (n = 406) over the dynamic range of the AxSYM assay demonstrated good correlation, r = 0.881, with a proportional bias: AxSYM cTnI = 3.50(Stratus cTnI) - 1. 10. The confidence intervals (95%) for the slope and intercept were 3.39-3.64 and -1.32 to -0.95, respectively. The expected cTnI concentration in healthy individuals was =0.5 microgram/L, whereas the ROC curve-determined cutoff for AMI was 2.0 microgram/L. This gave a diagnostic sensitivity of 91.8% and specificity of 92.4% when tested in serial samples collected within 24 h of admission in 633 patients presenting with chest pain, of which 122 had an AMI. The concordances of the AxSYM cTnI with the Stratus cTnI, OPUS cTnI, and Access cTnI were 95.3%, 95.1%, and 94.3%, respectively, from patients with suspected AMI. The AxSYM cTnI demonstrated excellent clinical specificity, >/=96%, in skeletal muscle injury, chronic renal disease, and same-day noncardiac surgery patients.