Table 4.

The screening potential of serum procalcitonin, C-reactive protein, white blood cell count, and erythrocyte sedimentation rate for detecting bacterial infections and strictly bacterial infections in patients with rheumatoid arthritis. Bacterial infection was finally diagnosed based on symptoms, bacterial culture tests, imaging studies, and response to antibiotic therapy. Strictly bacterial infection was diagnosed based on bacterial culture tests and/or imaging studies. OR, 95% CI, and p values were calculated by nonadjusted logistic regression analysis.

	Positive		Negative						Perdictive Value %		Likelihood Ratio
Condition	True	False	True	False	OR (95% CI)	p	Sensitivity, %	Specificity, %	Positive	Negative	Positive	Negative
Prevalence of bacterial infections = 52.5%
PCT ≥ 0.2 ng/ml	21	6	50	41	4.27 (1.58, 11.57)	0.004	33.9	89.3	77.8	54.9	3.17	1.35
PCT ≥ 0.5 ng/ml	16	1	55	46	19.13 (2.44, 149.78)	0.005	25.8	98.2	94.1	54.5	14.33	1.32
CRP ≥ 0.3 mg/dl	60	53	3	2	1.70 (0.27, 10.55)	0.570	96.8	5.4	53.1	60.0	0.03	1.69
WBC > 8500/mm³	41	23	33	21	2.80 (1.33, 5.92)	0.007	66.1	58.9	64.1	61.1	1.61	1.74
ESR > 15 mm/h	53	41	4	1	5.17 (0.56, 48.03)	0.149	98.1	8.9	56.4	80.0	0.02	4.68
PCT ≥ 0.5 ng/ml and WBC > 8500/mm³	13	1	55	49	14.59 (1.84, 115.65)	0.011	21.0	98.2	92.9	52.9	11.67	1.24
Prevalence of strictly bacterial infections = 41.5%
PCT ≥ 0.5 ng/ml	12	5	64	37	4.15 (1.36, 12.71)	0.013	24.2	92.8	70.6	63.4	3.38	1.23
CRP ≥ 0.3 mg/dl	47	66	3	2	1.07 (0.17, 6.64)	0.944	95.9	4.3	41.6	60.0	1.00	1.07
WBC > 8500/mm³	32	32	37	17	2.18 (1.02, 4.63)	0.043	65.3	53.6	50.0	68.5	1.41	1.55
ESR > 15 mm/h	41	53	5	0	∞ (0.00, ∞)	0.340	100.0	8.6	43.6	100.0	0.00	0.00

PCT: serum procalcitonin; CRP: C-reactive protein; WBC: white blood cell count; ESR: erythrocyte sedimentation rate.