Table 2 Diagnostic performance of the clinical prediction models

A: C-statistics of the logistic regression models

Original model (95%-CI)

Updated model (95%-CI)

Feverkidstool (n = 8049)

Pneumonia

0.80 (0.77–0.84)

0.83 (0.80–0.86)

Other SBI

0.74 (0.70–0.79)

0.78 (0.74–0.83)

Craig model (n = 8211)

Pneumonia

0.80 (0.77–0.83)

0.83 (0.80–0.86)

Complicated UTI

0.75 (0.70–0.80)

0.86 (0.83–0.90)

Bacteraemia

0.63 (0.39–0.88)

0.80 (0.66–0.94)

SBI-model (n = 8049)

0.66 (0.59–0.73)

0.67 (0.60–0.73)

B: Calibration intercepts and calibration slopes of the logistic regression models

Original model

Updated model

Calibration intercept (95%-CI)

Calibration slope (95%-CI)

Calibration intercept (95%-CI)

Calibration slope (95%-CI)

Feverkidstool

 Pneumonia vs. absence of SBI

0.09 (− 0.07 to 0.24)

1.01 (0.87 to 1.14)

0.00 (− 0.16 to 0.16)

1.04 (0.92 to 1.17)

 Other SBI vs. absence of SBI

 − 2.76 (− 2.96 to − 2.56)

0.50 (0.38 to 61)

0.00 (− 0.20 to 0.20)

1.05 (0.86 to 1.25)

Craig model

 Pneumonia vs. absence of SBI

 − 0.87 (− 1.03 to − 0.71)

0.72 (0.63 to 0.81)

0.00 (− 0.16 to 0.16)

1.05 (0.93 to 1.18)

 Complicated UTI vs. absence of SBI

 − 1.33 (− 1.59 to − 1.06)

0.69 (0.49 to 0.88)

0.00 (− 0.26 to 0.26)

1.27 (1.00 to 1.55)

 Bacteraemia vs. absence of SBI

 − 1.31 (− 2.06 to − 0.55)

0.30 (− 0.10 to 0.71)

0.00 (− 0.75 to 0.75)

0.34 (0.02 to 0.65)

SBI model

 − 4.97 (− 5.10 to − 4.85)

0.71 (0.60 to 0.83)

0.00 (− 0.12 to 0.12)

1.03 (0.87 to 1.20)

C: Diagnostic test parameters for updated regression models and original risk scores

Sensitivity (95%-CI)

Specificity (95%-CI)

LR( +) (95%-CI)

LR( −) (95%-CI)

Updated Feverkidstool

 Pneumonia

  Risk ≥ 2.5%

0.71 (0.64–0.78)

0.77 (0.76–0.78)

3.09 (2.79–3.42)

0.37 (0.29–0.47)

  Risk ≥ 10%

0.29 (0.22–0.36)

0.98 (0.97–0.98)

12.40 (9.41–16.36)

0.73 (0.66–0.80)

  Risk ≥ 30%

0.08 (0.04–0.13)

1.00 (1.00–1.00)

31.52 (15.83–62.78)

0.93 (0.89–0.97)

 Other SBI

  Risk ≥ 2.5%

0.51 (0.41–0.61)

0.87 (0.86–0.88)

3.91 (3.21–4.75)

0.56 (0.46–0.68)

  Risk ≥ 10%

0.04 (0.01–0.10)

1.00 (0.99–1.00)

10.29 (3.69–28.67)

0.96 (0.93–1.00)

  Risk ≥ 30%

0 (0–0.04)

1 (1–1)

NA

1 (1–1)

Updated Craig model

 Pneumonia

  Risk ≥ 2.5%

0.69 (0.61–0.76)

0.81 (0.80–0.81)

3.56 (3.19–3.97)

0.38 (0.31–0.48)

  Risk ≥ 10%

0.27 (0.21–0.35)

0.97 (0.97–0.98)

10.89 (8.24–14.39)

0.74 (0.68–0.82)

  Risk ≥ 30%

0.08 (0.04–0.13)

1.00 (1.00–1.00)

43.66 (20.84–91.47)

0.93 (0.89–0.97)

 Complicated UTI

  Risk ≥ 2.5%

0.23 (0.13–0.36)

0.96 (0.95–0.96)

5.62 (3.45–9.16)

0.80 (0.70–0.93)

  Risk ≥ 10%

0.04 (0.00–0.12)

1.00 (1.00–1.00)

40.87 (8.68–192.51)

0.97 (0.92–1.01)

  Risk ≥ 30%

0 (0–0.06)

1 (1–1)

NA

1 (1–1.00)

 Bacteraemia

  Risk ≥ 2.5%

0 (0–0.41)

1.00 (1.00–1.00)

0 (0–0.13)

1.00 (1.00–1.00)

  Risk ≥ 10%

0 (0–0.41)

1.00 (1.00–1.00)

0 (0–0.97)

1.00 (1.00–1.00)

  Risk ≥ 30%

0 (0–0)

1 (1–1)

NA

1 (1–1)

Updated SBI model

 Risk ≥ 2.5%

0.93 (0.89–0.95)

0.25 (0.24–0.26)

1.23 (1.19–1.27)

0.30 (0.19–0.45)

 Risk ≥ 10%

0.11 (0.07–0.15)

0.98 (0.98–0.99)

6.23 (4.25–9.15)

0.91 (0.87–0.95)

 Risk ≥ 30%

0.01 (0.00–0.03)

1.00 (1.00–1.00)

3.78 (0.87–16.46)

0.99 (0.98–1.00)

SBI score

 Score ≤ 5

0.11 (0.08–0.15)

0.98 (0.98–0.98)

5.81 (4.15–8.15)

0.90 (0.87–0.94)

 Score > 8

0.01 (0.00–0.02)

1.00 (1.00–1.00)

4.20 (0.93–18.87)

0.99 (0.98–1.00)

PAWS

 Score ≥ 3

0.32 (0.28–0.37)

0.86 (0.85–0.87)

2.28 (1.98–2.61)

0.79 (0.74–0.84)