The Clinical Diagnostic Values of SAA, PCT, CRP, and IL-6 in Children with Bacterial, Viral, or Co-Infections

Figures & data

Table 1 Clinicopathologic Characteristics of the Patients and Healthy Controls

Variable	Heathy Control (n=42)	Bacterial (n=46)	Virus (n=7)	Bacterial+Virus (n=128)	P value
Gender,male	26 (61.90%)	25 (52.17%)	3 (42.86%)	73 (57.03%)	0.773
Age, year	1.69±1.20	1.23±1.21	1.32±0.69	1.69±0.96	0.0713

Table 2 Infection Symptoms of the Patients

	Bacterial (n=46)	Virus (n=7)	Bacterial+Virus (n=128)
Respiratory tract infection	38 (82.61%)	6 (85.71%)	91 (71.09%)
Influenza	3 (6.52%)	–	8 (6.25%)
Septicopyemia	2 (4.35%)	–	5 (3.91%)
Fever	1 (2.17%)	–	2 (1.56%)
Intestinal infection	2 (4.35%)	1 (14.29%)	5 (3.91%)
Ballismus	–	–	3 (2.34%)
Convulsion	–	–	7 (5.47%)
Others	–	–	7 (5.47%)

Figure 1 Analysis for the levels of serum biochemical biomarkers in children with bacterial, viral, or co-infections. (A) The level of serum SAA in children with bacterial, viral, or co-infections. (B) The level of serum PCT in children with bacterial, viral, or co-infections. (C) The level of serum IL-6 in children with bacterial, viral, or co-infections. (D) The level of serum CRP in children with bacterial, viral, or co-infections.

Table 3 Sensitivity and Specificity of SAA, PCT, CRP, and IL-6 in Different Groups

Group	Biomarker	Cut-off	AUC	Sensitivity (%)	Specificity (%)	95% CI	P value
HC of Bac	SAA	>5.56	0.5417	8.33	100	0.4225–0.6608	0.4969
	PCT	>0.055	0.9281	86.96	100	0.8645–0.9916	<0.0001
	CRP	>0.405	0.8383	65.22	83.33	0.7558–0.9207	<0.0001
	IL-6	>6.18	0.7751	69.57	78.57	0.6647–0.8828	<0.0001
HC of Bac + Vir	SAA	>7.53	1	100	100	1–1	<0.0001
	PCT	>0.055	0.9961	99.22	100	0.9882–1.004	<0.0001
	CRP	>1.025	0.9958	97.66	100	0.9894–1.002	<0.0001
	IL-6	>6.42	0.9588	94.53	95.24	0.9278–0.9898	<0.0001
Bac to Bac + Vir	SAA	>10.13	1	100	100	1–1	<0.0001
	PCT	>0.155	0.8060	64.06	80.43	0.7365–0.8756	<0.0001
	CRP	>2.465	0.9745	90.63	97.83	0.9545–0.9946	<0.0001
	IL-6	>18.02	0.8145	67.97	78.26	0.7405–0.8885	<0.0001

Abbreviations: HC, healthy control; Bac, bacterial infection; Bac + Vir, bacterial and viral co-infections; SAA, serum amyloid A; PCT, procalcitonin; CRP, C-reactive protein; IL-6, interleukin-6.

Figure 2 Diagnostic values of serum biochemical biomarkers in children with bacterial, viral, or co-infections. (A) ROC curves for SAA, PCT, IL-6, and CRP for discrimination between bacterial infection and healthy control. (B) ROC curves for SAA, PCT, IL-6, and CRP for discrimination between co-infection and healthy control. (C) ROC curves for SAA, PCT, IL-6, and CRP for discrimination between co-infection and bacterial infection.