Risk factors for surgical site infection in a teaching hospital: a prospective study of 1,138 patients

Figures & data

Table 1 Analysis of patient factors related to surgical site infections using the chi-square test

Risk factor (n)	Infection cases (incidence, %)	χ^2 (P-value)
Sex
Male (542)	19 (3.5)	0.089
Female (596)	19 (3.2)	(0.776)
Age (years)
<75 (977)	29 (3.0)	2.944
≥75 (161)	9 (5.6)	(0.086)
Pre-morbidity
Diabetes
Yes (77)	11 (14.3)	30.660
No (1,061)	27 (2.5)	(0.000)
Cancer
Yes (119)	10 (8.4)	10.559
No (1,019)	28 (2.7)	(0.001)
Wound classification
Clean (639)	3 (0.5)
Clean contaminated (379)	24 (6.3)	60.768
Contaminated (112)	8 (7.1)	(0.000)
Dirty (8)	3 (37.5)
ASA score before operation
Level I (387)	3 (0.8)
Level II (576)	19 (3.3)	33.411
Level III (139)	13 (9.4)	(0.000)
Level IV (9)	2 (22.2)
Level V (27)	1 (3.7)
Skin preparation
Yes (423)	13 (3.1)	0.147
No (715)	25 (3.5)	(0.701)
Preprocedural WBC (×10^9/L)
≤10 (988)	20 (2.0)	40.151
>10 (150)	18 (12.0)	(0.000)
Type of surgery
Selective (972)	24 (2.5)	15.628
Emergency (166)	14 (8.4)	(0.000)
Type of anesthesia
General anesthesia (812)	32 (3.9)	4.225
Balanced anesthesia (48)	2 (4.2)	(0.376)
Epidural anesthesia (13)	0 (0.0)
Local anesthesia (263)	4 (1.5)
Other (2)	0 (0.00)
Volume of blood loss (mL)
<200 (869)	19 (2.2)	18.057
200–400 (213)	13 (6.1)	(0.000)
≥400 (56)	6 (10.7)
Blood transfusion
Yes (56)	6 (10.7)	9.925
No (1,082)	32 (3.0)	(0.002)
Risk index
0 (673)	9 (1.3)
1 (377)	22 (5.8)	22.001
2 (78)	4 (5.1)	(<0.000)
3 (10)	3 (30.0)
Operative duration (minutes)
<120 (553)	8 (1.4)	11.937
≥120 (585)	30 (5.1)	(0.001)
Catheter
Gastrointestinal catheter
Yes (353)	25 (7.1)	22.212
No (785)	13 (1.7)	(0.000)
Urinary catheters
Yes (421)	23 (2.1)	9.339
No (717)	15 (5.5)	(0.002)
Trachea cannula
Yes (402)	13 (3.2)	0.021
No (736)	25 (3.4)	(0.884)
Postoperative drainage
Yes (539)	33 (6.1)	24.576
No (599)	5 (0.8)	(0.000)
Antibiotic prophylaxis
Yes (944)	28 (3.0)	2.388
No (194)	10 (5.2)	(0.122)

Abbreviations: ASA, American Society of Anesthesiologists; WBC, white blood cell count.

Table 2 Analysis of risk factors for surgical site infection using a multivariate logistic regression model

Risk factor	Variables in the equation						Reference
	β	SE	Wald	P-value	OR	95% CI
Diabetes	1.856	0.463	16.059	0.000	6.400	2.582–15.866	No
Cancer	0.887	0.438	4.093	0.043	2.427	1.028–5.732	No
Preprocedural WBC (×10^9/L)
>10	1.944	0.404	23.157	0.000	6.988	3.165–15.425	≤10
Wound classification
Clean contaminated	2.066	0.642	10.364	0.001	7.893	2.244–27.762	Clean
Contaminated	1.950	0.739	6.966	0.008	7.031	1.652–29.922
Dirty	3.887	1.121	12.020	0.001	48.778	5.418–439.164
Operative duration (minutes)
≥120	1.456	0.451	10.433	0.001	4.289	1.773–10.378	<120
Postoperative drainage	1.375	0.522	6.942	0.008	3.957	1.422–11.008	No

Notes: β indicates the partial regression coefficient, and 95% CI is credibility interval of 95% standard partial regression coefficient.

Abbreviations: CI, confidence interval; OR, odds ratio; SE, standard error; WBC, white blood cell count.