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 1	Novel quintet 2
	Ayoub and Ahmed	Modification 1	Modification 2	Modification 3	Modification 4
	A, B, C, D, E	A, B, C, D, E, F	A, B, C, D, E, G	A, C, D, E, F	A, C, D, F, G
Se	50%	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 3	9–86%	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