DISCUSSION

We present an innovative computer-assisted surveillance system that combines direct observation during hospital stay with a thorough follow-up after discharge. A central component of the system is daily inspection of the surgical wound by the attending physician and mandatory reporting in the patient’s electronic medical chart. Follow-up after discharge included outpatient clinic visit data, a structured phone interview, and review of readmission data. We found that reviewing only readmission data was highly sensitive for postdischarge SSI detection and therefore precluded the need for outpatient clinic visit data and phone interview. Using this combined method enabled us to perform highly accurate continuous surveillance with relatively few human resources. This routine and permanent SSI surveillance is unique in Israel and allows us to provide periodic feedback to the surgeons concerning SSI rates.

Most postoperative infections occur after discharge, especially when the initial hospitalization is short.Reference Edwards, Peterson and Mu ^{6 ,} Reference Ward, Charlett, Fagan and Crawshaw ⁹ In our study, 78% of postoperative infections occurred after discharge; therefore, our monitoring system included comprehensive postdischarge surveillance. Postdischarge follow-up at several stages as well as high rates of completion of the follow-up during hospitalization increases the sensitivity of the monitoring and strengthens the confidence in its accuracy and validity. Nearly all infections identified after discharge, 120 of 128 (94%), were detected upon readmission or emergency department visits. We found that the sensitivity of surveillance, which includes follow-up during hospitalization and assessment of readmission data, is 95.5%. This high value allows us to dispense with assessment of the outpatient clinic and phone calls and to use rehospitalization only for postdischarge follow-up. This method, while maintaining high sensitivity of SSI detection, reduces the proportion of patients who need assessment after discharge to 30% (those who returned to the emergency room or were hospitalized within 3 months). In our orthopedic department, patients return to the hospital according to the instructions they receive, even for the slightest suspicion of infection, and this policy enables us to rely on readmission only.

We developed a computerized system that enables us to collect a significant part of the SSI data automatically. Furthermore, physicians are required to report wound status daily during morning visits, and these data are stored in the computerized file. Rehospitalization is recorded automatically in the same file, which eases the identification of patient records that should be further assessed. The system can be further improved by adding a mandatory field for wound status upon readmission. However, a system administrator is needed to operate the system and to analyze the data.Reference Klompas and Yokoe ^{4 ,} Reference Lower, Eriksen, Aavitsland and Skjeldestad ¹⁰

Regarding our SSI rates, we did not find an overall decline in infections over these 5 study years. Perhaps this is because the underlying deep infection rate was low, as reflected in the comparison of our infection rate with the NHSN data.Reference Edwards, Peterson and Mu ⁶ It is also possible that sensitivity increased with the development of the monitoring system. Another possible explanation is that the staff received feedback only once a year, which makes potential corrective actions difficult. Providing more frequent feedback may lead to corrective actions, which in turn may yield a reduction in SSI rate. Using statistical process control presented by a g-type control chart,Reference Benneyan, Lloyd and Plsek ⁸ feedback can be provided more frequently and continuously.

A comparison of the SSI rates detected by our surveillance system with those found through diagnoses codes for infection in the discharge and readmission letters showed very low sensitivity (34.5%) and indicates a low accuracy of diagnoses codes regarding SSI in discharge letters at our institution.

The study has several limitations. First, the reliability of postdischarge SSI detection by readmission only might not be widely applicable. It may be restricted to a system in which patients are instructed to return to the hospital in which the surgery was performed, as actually occurs in our hospital. Second, because the hospital surveillance is performed by the residents and not by an external observer, it is reliable only after thorough instruction of the physicians and assurance that their reporting is accurate. The mandatorily daily recording of wound status by the attending physician during hospitalization lowers the chance of omitting patient data from the medical record.

In summary, we created a semiautomatic surveillance system assisted by the surgeons for in-hospital wound follow-up. The fact that almost every patient who developed SSI after discharge was readmitted allows limiting postdischarge follow-up to patients who were readmitted, thus significantly reducing the workload without reducing surveillance accuracy. The principles of this model can be adopted by other hospitals if physician reports are valid and if the readmission policy is similar to the one described in this study.