Table 3

Sensitivities, specificities and likelihood ratios for laboratory findings

Serum laboratory values	Study	Prevalence of SA, %	Sensitivity (95% CI)	Specificity (95% CI)	Likelihood ratio (95% CI)
Serum laboratory values	Study	Prevalence of SA, %	Sensitivity (95% CI)	Specificity (95% CI)	Positive (LR+)	Negative (LR−)
White blood cell count (WBC)
WBC bands ≥350/mm³	Del Beccaro et al22	31.2	0.53 (0.35 to 0.70)	0.75 (0.64 to 0.84)	2.1 (1.3 to 3.4)	0.6 (0.4 to 0.9)
≥11.0×10⁹/L	Jung et al23	21.8	0.74 (0.54 to 0.89)	0.94 (0.87 to 0.98)	12.0 (5.4 to 26.8)	0.3 (0.2 to 0.5)
≥12.0×10⁹/L	Caird et al18	70.8	0.50 (0.32 to 0.68)	0.71 (0.42 to 0.92)	1.8 (0.7 to 4.3)	0.7 (0.4 to 1.1)
	Heyworth et al12	32.6	0.47 (0.21 to 0.73)	0.55 (0.36 to 0.73)	1.0 (0.5 to 2.0)	1.0 (0.6 to 1.7)
	Sultan et al21	5.2	0.40 (0.05 to 0.85)	0.81 (0.72 to 0.89)	2.1 (0.7 to 6.8)	0.7 (0.4 to 1.5)
≥15.0×10⁹/L	Del Beccaro et al22	29.2	0.26 (0.13 to 0.43)	0.84 (0.75 to 0.91)	1.6 (0.8 to 3.3)	0.9 (0.7 to 1.1)
≥15.0×10⁹/L	Kuda et al24	27.3	0.78 (0.40 to 0.97)	0.75 (0.53 to 0.90)	3.1 (1.4 to 6.8)	0.3 (0.1 to 1.0)
Erythrocyte sedimentation rate (ESR)
>20 mm/hour	Del Beccaro et al22	29.2	0.79 (0.63 to 0.90)	0.72 (0.61 to 0.81)	2.8 (1.9 to 4.0)	0.3 (0.2 to 0.6)
	Jung et al23	21.8	0.93 (0.76 to 0.99)	0.59 (0.48 to 0.69)	2.3 (1.7 to 2.9)	0.1 (0.0 to 0.5)
	Kuda et al24	27.3	1.00 (0.66 to 1.00)	0.75 (0.53 to 0.90)	4.0 (2.0 to 8.0)	NA
>25 mm/hour	Levine et al20	31.5	0.92 (0.79 to 0.98)	0.22 (0.14 to 0.33)	1.2 (1.0 to 1.4)	0.3 (0.1 to 1.1)
>30 mm/hour	Del Beccaro et al22	29.2	0.71 (0.54 to 0.85)	0.86 (0.77 to 0.92)	5.0 (2.9 to 8.7)	0.3 (0.2 to 0.6)
>40 mm/hour	Caird et al18	70.8	0.56 (0.38 to 0.73)	0.86 (0.57 to 0.98)	3.9 (1.1 to 14.6)	0.5 (0.3 to 0.8)
	Heyworth et al12	32.6	0.53 (0.27 to 0.79)	0.58 (0.39 to 0.75)	1.3 (0.7 to 2.4)	0.8 (0.4 to 1.5)
	Jung et al23	21.8	0.74 (0.54 to 0.89)	0.94 (0.87 to 0.98)	12.0 (5.4 to 26.8)	0.3 (0.2 to 0.5)
	Sultan et al21	5.2	0.40 (0.05 to 0.85)	0.88 (0.79 to 0.84)	3.3 (1.0 to 11.1)	0.7 (0.3 to 1.4)
>50 mm/hour	Kuda et al24	27.3	0.67 (0.30 to 0.93)	0.92 (0.73 to 0.99)	8.0 (2.0 to 32.6)	0.4 (0.1 to 0.9)
>75 mm/hour	Levine et al20	31.5	0.26 (0.13 to 0.42)	0.87 (0.78 to 0.93)	2.0 (0.9 to 4.3)	0.9 (0.7 to 1.1)
C reactive protein (CRP)
>7 mg/L	Heyworth et al12	31	1.00 (0.75 to 1.00)	0.14 (0.04 to 0.32)	1.2 (1.0 to 1.3)	NA
>10 mg/L	Jung et al23	21.8	0.89 (0.71 to 0.98)	0.93 (0.86 to 0.97)	12.3 (6.0 to 25.5)	0.1 (0.0 to 0.4)
>10 mg/L	Levine et al20	29.3	0.90 (0.76 to 0.97)	0.29 (0.20 to 0.39)	1.3 (1.1 to 1.5)	0.4 (0.1 to 1.0)
>20 mg/L	Caird et al18	70.8	0.85 (0.69 to 0.95)	0.71 (0.42 to 0.92)	3.0 (1.3 to 6.9)	0.2 (0.1 to 0.5)
>20 mg/L	Sultan et al21	5.2	0.60 (0.15 to 0.95)	0.90 (0.82 to 0.95)	6.1 (2.4 to 15.6)	0.4 (0.2 to 1.3)
>50 mg/L	Levine et al20	29.3	0.67 (0.50 to 0.81)	0.67 (0.57 to 0.76)	2.0 (1.4 to 2.9)	0.5 (0.3 to 0.8)
>105 mg/L	Levine et al20	29.3	0.41 (0.26 to 0.58)	0.85 (0.76 to 0.92)	2.8 (1.5 to 5.1)	0.7 (0.5 to 0.9)
Serum procalcitonin
>0.5 ng/mL	Faesch et al11	14.2	0.13 (0.05 to 0.25)	0.97 (0.94 to 0.99)	4.0 (1.5 to 10.8)	0.9 (0.8 to 1.0)
Synovial fluid WBC count
≥40 000 cells/μL	Deanehan et al17	4.6	0.65 (0.38 to 0.86)	0.46 (0.40 to 0.51)	1.2 (0.8 to 1.7)	0.8 (0.4 to 1.5)
50 000 cells/μL	Deanehan et al17	4.6	0.41 (0.18 to 0.67)	0.59 (0.54 to 0.64)	1.0 (0.6 to 1.8)	1.0 (0.7 to 1.5)
≥75 000 cells/μL	Deanehan et al17	4.6	0.29 (0.10 to 0.56)	0.79 (0.74 to 0.83)	1.4 (0.6 to 3.0)	0.9 (0.7 to 1.2)
≥100 000 cells/μL	Deanehan et al17	4.6	0.24 (0.07 to 0.50)	0.89 (0.85 to 0.92)	2.2 (0.9 to 5.3)	0.9 (0.7 to 1.1)
25 000–50 000 cells/mm³	Heyworth et al12	32.6	0.27 (0.08 to 0.55)	0.39 (0.22 to 0.58)	0.4 (0.2 to 1.1)	1.9 (1.1 to 3.2)
50 000–75 000 cells/mm³	Heyworth et al12	32.6	0.73 (0.45 to 0.92)	0.61 (0.42 to 0.78)	1.9 (1.1 to 3.2)	0.4 (0.2 to 1.1)

NA, not available.