C-Reactive Protein Level as Diagnostic Marker in Young Febrile Children Presenting in a General Practice Out-of-Hours Service

Marijke Kool; Gijs Elshout; Bart W. Koes; Arthur M. Bohnen; Marjolein Y. Berger

doi:10.3122/jabfm.2016.04.150315

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Figure 1.
Flowchart of inclusion of all eligible children. CRP, C-reactive protein; OHS, out-of-hours service.

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Table 1.

Characteristics of Children with (n = 440) and without (n = 66) C-Reactive Protein Measurement (CRP)

	Children with CRP measured (n = 440)	Children without CRP measured (n = 66)
Age (months)^*
Mean (SD)	25 (17)	30 (18)
Median (range)	20 (3–70)	28 (3–66)
Male sex	254 (57.7)	35 (53.0)
Immigrant (yes)	228 (51.8)	31 (47.0)
Face-to-face contact with a general practitioner at presentation	327 (74.3)	44 (66.7)
Antibiotic prescriptions before presentation	37 (8.4)	7 (10.6)
Referral at initial presentation^{^†}	18 (4.1)	8 (12.1)
Serious illness at presentation^{^‡}	25 (5.7)	8 (12.1)
SI at presentation^{^§}	30 (6.8)	10 (15.2)
Referral after 1 week	34 (7.7)	8 (12.1)
Serious illness after 1 week	39 (8.9)	8 (12.1)
SI after 1 week	50 (11.4)	10 (15.2)
Antibiotic prescriptions after 1 week	181/432 (41.9)	23/58 (39.7)

Data are n (%) unless otherwise indicated.
↵* Significant difference (mean difference, 5.7; 95% confidence interval, 1.2–10.1).
↵† Significant difference (χ² = 7.593; df = 1; P = 0.006)
↵‡ Significant difference (χ² = 3.904; df = 1; P = 0.048)
↵§ Significant difference (χ² = 5.474; df = 1; P = 0.019).
SD, standard deviation; SI, serious infection (defined as a serious illness or referral).

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Table 2.

Sensitivities and Specificities for Detecting Serious Infection (n = 50) or No Serious Infection (n = 390) Among All Children with C-Reactive Protein (CRP) Measurement (n = 440)

	SI (n = 50)		No SI (n = 390)		Sensitivity (95% CI)	Specificity (95% CI)	Positive Predictive Value (95% CI)	Negative Predictive Value (95% CI)	LR+	LR−
	Yes	No	Yes	No	Sensitivity (95% CI)	Specificity (95% CI)	Positive Predictive Value (95% CI)	Negative Predictive Value (95% CI)	LR+	LR−
CRP >20 mg/L	26	24	182	208	52.0 (38.2–65.8)	53.3 (48.4–58.3)	12.5 (8.0–17.0)	89.7 (85.7–93.6)	1.1 (0.8–1.5)	0.9 (0.7–1.2)
CRP >80 mg/L	14	36	52	338	28.8 (15.6–40.4)	86.7 (83.3–90.0)	21.2 (11.3–31.1)	90.4 (87.4–93.4)	2.1 (1.3–3.5)	0.8 (0.7–1.2)

CI, confidence interval; LR+, positive likelihood ratio; LR−, negative likelihood ratio; SI, serious infection (defined as serious illness or referral).

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Table 3.

Sensitivities and Specificities for Detecting Serious Infection During Follow-up (n = 20) or No Serious Infection During Follow-up (n = 390) Among Children Who Had No Serious Infection at Presentation (n = 410)

	SI (n = 20)		No SI (n = 390)		Sensitivity (95% CI)	Specificity (95% CI)	Positive Predictive Value (95% CI)	Negative Predictive Value (95% CI)	LR+	LR−
	Yes	No	Yes	No	Sensitivity (95% CI)	Specificity (95% CI)	Positive Predictive Value (95% CI)	Negative Predictive Value (95% CI)	LR+	LR−
CRP > 20 mg/L	9	11	182	208	45.0 (23.2–66.8)	53.3 (48.4–58.3)	4.7 (1.7–7.7)	95.0 (92.1–97.9)	1.0 (0.6–1.6)	1.0 (0.7–1.5)
CRP > 80 mg/L	5	15	52	338	25.0 (6.0–44.0)	86.7 (83.3–90.0)	8.8 (1.4–16.1)	95.0 (92.1–97.9)	1.9 (0.8–4.2)	0.9 (0.7–1.1)

CI, confidence interval; CRP, C-reactive protein; LR+, positive likelihood ratio; LR−, negative likelihood ratio; SI, serious infection (defined as serious illness or referral).