From:  Diagnostic performance and cutoff optimisation of the CTD Screen assay for ANA detection compared with HEp-2 IFA

 Test performance of the CTD Screen assay.

CTD Screen performanceWith the manufacturer cutoffWith a modified cutoffHEp-2 IFA
Sensitivity (95% CI)73.9%81.5%73.7%
Specificity (95% CI)92.6%85.6%71.1
LR+ (95% CI)9.935.652.56
LR– (95% CI)0.280.220.37
PPV (95% CI)82.8%73.3%77.2%
NPV (95% CI)87.9%90.5%67.1%
Accuracy (95% CI)86.4%84.2%72.6%
κ (95% CI)0.6830.6520.455

95% CI: 95% confidence intervals; CTD Screen: connective tissue disease Screen; HEp-2 IFA: HEp-2 cell indirect immunofluorescence assay; LR: likelihood ratio; NPV: negative predictive value; PPV: positive predictive value; κ: Cohen’s kappa.