[Increase in costs attributable to surgical infection after appendicectomy and colectomy]

To determine the costs, with the help of direct case to case measurement, of the surgical site infection in apendicectomy and colectomy.

cases and controls study, population-based, in which the cases were all the patients diagnosed of surgical site infection after apendicectomy or colectomy in SCIAS- Hospital de Barcelona, and the controls were a random sample of noninfected patients that presented common characteristics for matching purposes.

from January 1, 1998, to December 31, 1999. Types of matching: a) individual, patients grouped according to main diagnosis, main surgical procedure, age and gender, and b) patients grouped according to main diagnosis, main surgical procedure, age and gender using in addition, as controls criteria, the number of secondary diagnoses.

computer system with all the registries and clinical histories in electronic support, including the costs registered in real time. ANALYTICAL ACCOUNTING: ADS plus program that calculated the real costs (patient to patient) extracted from real data, such as drugs consumption, medical supplies, additional diagnosis tests and generated stays. The structural costs were imputed in the matrix of costs from the countable calculation and its impact on the direct costs. The cost attributable to the infection was calculated as the additional cost resultant from the difference between cases and controls.

the statistical calculations were made by means of the statistical package SPSS, version 9.0. Nonparametric tests were used considering the sample size. The test of Wilcoxon for continuous variables, with the purpose of comparing age, operations length, hospital stay and costs, was applied. The results were expressed as arithmetic mean. A level of statistical meaning of p < 0.01 was considered.

The first matching included 23 cases and 23 controls for patients operated on apendicectomy and 20 cases and 20 controls for those operated on colectomy. In matching 2, the sample consisted on 17 pairs of cases and controls on apendicectomy and 14 pairs of cases and controls on colectomy. The infection increased the average length of stay between 7.7 days (matching 1) and 7.3 days (matching 2) in cases of infected apendicectomy and between 17.6 days (matching 1) and 15.4 days (matching 2) in cases of infected colectomy. The patients with apendicectomy infection presented an average cost three times higher than the ones not infected, both in matching 1 (2,998.60 versus 941.89;, respectively; p < 0.0001) and in matching 2 (2,751.70 versus 870.81;, respectively; p < 0.0001). Similar findings were observed in colectomy both in matching 1 (10,705.34 versus 2,600.55;, respectively; p < 0.0001) and in matching 2 (9,081.12 versus 2,621.39;, respectively; p < 0.0001). The average cost of surgical site infection oscillated between 2,056.71; (matching 1) and 1,880.89; (matching 2) in apendicectomy and between 8,140.79; (matching 1) and 6,405.65; (matching 2) in colectomy.

Under the study conditions, the infection of surgical site determines the prolongation of the hospital stay in more than one week in apendicectomy and in more than two in colectomy, with an increase higher than 300% in the total direct cost.