International Journal of Rheumatology / 2009 / Article / Tab 2

Research Article

Differentiation of PSRA due to Group A and due to Nongroup A Streptococci in Patients with Early Arthritis and Elevated Antisteptolysin-O at Presentation

Table 2

Test characteristics of three sets applied as diagnostic criteria in 45 patients consisting of 36 patients with definite post-streptococcal reactive arthritis (PSRA) due to group A streptococci (GAS: n = 20) and due to nongroup A streptococci (NGAS: n = 16), and 9 non-PSRA patients: calculations represent values of a screening test aiming to find GAS-related PSRA only. Legend: Sensitivity (Se); Specificity (Sp); Positive Predictive Value (PPV); Negative Predictive Value (NPV); Likelihood ratio (LR+) in an ideal test is optimal when ad infinitum, as it gives a ratio between probability on a positive test result in GAS-induced PSRA patients versus nonindex patients; Likelihood ratio negative test (LR−) in an ideal test is optimal when it reaches nil, as it gives a ratio between probability on a negative test result in GAS-induced PSRA versus nonindex patients. In the second line 95% confidence intervals (95%CI) are given. For criteria (A), (B), (C), and so forth see also text in Materials and Methods section.

Set Original quintet Sextet 1 Sextet 2 Novel quintet 1Novel quintet 2
Ayoub and Ahmed Modification 1Modification 2Modification 3 Modification 4
A, B, C, D, E A, B, C, D, E, FA, B, C, D, E, GA, C, D, E, F A, C, D, F, G

Se50% 50% 50% 95% 95%
95%CI 28–72% 28–72% 28–72% 85–100% 85–100%
Sp 76% 88% 92% 88% 80%
95%CI 59–93% 75–100% 81–100% 75–100% 64–96%
PPV 63% 77% 83% 86% 79%
95%CI 39–86% 54–100% 62–100% 72–100% 63–95%
NPV 66% 69% 70% 96% 95%
95%CI 48–83% 53–85% 54–85% 87–100% 86–100%
LR+ 2.1 4.2 6.3 7.9 4.8
95%CI 0.9–4.7 1.3–13.2 1.5–25.3 2.7–23.0 2.9–7.7
LR- 0.66 0.57 0.54 0.06 0.06
95%CI 0.40–1.08 0.36–0.90 0.35–0.86 0.008–0.39 0.009–0.42

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