Ottawa Hospital Patient Safety Study: incidence and timing of adverse events in patients admitted to a Canadian teaching hospital

Interesting paper because of the innovation that reaches: more of the half of the adverse events happened before the hospitalization. Only 1 of every 5 were serious, but the character preventable were even major in the serious ones (41, 6 % opposite to 36,5 % in no serious, p > 0,05). They find a high incidence of adverse events (12, 7 %), surely lynked to the methodology of study that was looking for the maxim specificity (8 false positives found in the first review and 14 false negatives), lock at the exhaustively with which every case is described in the appendix. Provided that the major impact of the adverse events is precisely the death, it calls our attention that the design has not tried to detect associations between death and adverse events: how was mortality in adverse events absence? In this study all deaths were considered to be not avoidable, but, how about with absence of relationship between deaths and adverse events? It is possible that the used methodology subestimates the effect of adverse effects before the hospitalization, if these are detected when the patient have had to be hospitalized? Although it is expected that this infraestimation is due to no serious adverse events, that could have been solved without need to hospitalize the patient. The kind of retrospective study, made trough medical notes review, is common (1,2,3) but it does not appear to be the most adequate method for a precise estimation of adverse events, and it shows methodological limitations as demonstrates a paper that that compares in the same context three types of studies: cross-over, retrospective cohorts and prospective cohorts, founding the last the most appropriated for aspire to more precise adverse events detection(4). In our opinion, for a good accessibility National Health Care System, estimation of the adverse events before the hospitalization might be better with an combined analysis of Accident and Emergency Services. Finally, we think that the work of Alan J. Forster et al. offers a new route for the study of adverse events, which will make new preventive strategies possible.

Joaquin Beltran-Peribanez, Jesús Mª Aranaz Andrés

Departamento de Salud Pública, Historia de la Ciencia y Ginecología, Universidad Miguel Hernández. Campus de San Juan, Carretera de Valencia s/n, 03550-San Juan de Alicante. Alicante. Spain. Tfno: 965 919572. e- mail: quino@umh.es

References

1. Thomas EJ, Studdert DM, Burstin HR, et al. Incidence and types of adverse events and negligent care in Utah and Colorado. Med Care 2000;38:261-71.

2. Brennan TA, Leape LL, Laird NM, et al. Incidence of adverse events and negligence in hospitalised patients: Results of the Harvard Medical Practice Study I-II. N Engl J Med 1991;324:370-84.

3. Aranaz JM, Gea MT, Marín G. Acontecimientos adversos en un servicio de cirugía general y de aparato digestivo de un hospital universitario. Cir Esp 2003;73:104-9.

4. Michel P, Quenon JL, Sarasqueta AM, Scemama O. Comparison of three methods for estimating rates of adverse events and rates of preventable adverse events in acute care hospitals. Br J Med 2004;328:199-0.

Conflict of Interest:

None declared