Table 2 Sensitivity, specificity, predictive values, and likelihood ratios of the different laboratory parameters for the serious bacterial infection (SBI) and bacteraemia–sepsis groups
Sensitivity, % (95% CI)Specificity, % (95% CI)PPV, % (95% CI)NPV, % (95% CI)LR+LR−
SBI
  • Leucocyte count (/μl)

    >10 00073 (64 to 82)58 (52 to 64)35 (28 to 42)87 (82 to 92)1.70.46
    >15 00038 (28 to 48)84 (80 to 88)43 (32 to 54)81 (77 to 85)2.40.74
  • CRP (mg/l)

    ⩾2064 (54 to 74)84 (80 to 88)55 (45 to 65)88 (84 to 92)40.43
    ⩾3059 (48 to 70)89 (85 to 93)63 (52 to 74)87 (83 to 91)5.40.46
  • PCT-Q (ng/ml)

    ⩾0.563 (52 to 74)87 (83 to 91)59 (48 to 70)89 (85 to 93)4.80.42
  • Leucocyte count (>15 000) or CRP (⩾30) or PCT (⩾0.5)

84 (76 to 92)67 (61 to 73)45 (37 to 53)93 (89 to 97)2.50.24
  • Leucocyte count (5000–15 000), CRP (<30), PCT (<0.5), good general state and negative urine dipstick

96 (88 to 99)35 (29 to 42)32 (25 to 38)96 (92 to 100)1.480.11
Bacteraemia/sepsis
  • CRP >30 mg/l

56 (32 to 80)74 (69 to 79)9,6 (4 to 16)97 (95 to 99)2.150.59
  • PCT-Q >0.5 ng/ml

86 (58 to 100)93 (90 to 96)35 (19 to 51)99 (98 to 100)12.30.15
  • Leucocyte count (5000–15 000), CRP (<30), PCT (<0.5), good general state and negative urine dipstick

100 (74 to 100)29 (24 to 35)6 (3 to 9)100 (96 to 100)1.40
  • CRP, C reactive protein; LR, likelihood ratio; NPV, negative predictive value; PCT-Q, semiquantitative procalcitonin; PCT, procalcitonin; PPV, positive predictive value.