Open Access Research article

Estimating the incidence of adverse events in Portuguese hospitals: a contribution to improving quality and patient safety

Paulo Sousa1*, António Sousa Uva12, Florentino Serranheira12, Carla Nunes1 and Ema S Leite123

Author Affiliations

1 National School of Public Health, Universidade Nova de Lisboa, Avenida Padre Cruz, 1600-540 Lisboa, Portugal

2 CMDT – Centro de Investigação em Malária e Doenças Tropicais – Saúde Pública, Lisboa, Portugal

3 Centro Hospitalar de Lisboa Central, Lisboa, Portugal

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BMC Health Services Research 2014, 14:311  doi:10.1186/1472-6963-14-311

Published: 18 July 2014



Several review studies have shown that 3.4% to 16.6% of patients in acute care hospitals experience one or more adverse events. Adverse events (AEs) in hospitals constitute a significant problem with serious consequences and a challenge for public health. The occurrence of AEs in Portuguese hospitals has not yet been systematically studied. The main purpose of this study is to estimate the incidence, impact and preventability of adverse events in Portuguese hospitals. It is also our aim to examine the feasibility of applying to Portuguese acute hospitals the methodology of detecting AEs through record review, previously used in other countries.


This work is based on a retrospective cohort study and was carried out at three acute care hospitals in the Administrative Region of Lisbon. The identification of AEs and their impact was done using a two-stage structured retrospective medical records review based on the use of 18 screening criteria. A random sample of 1,669 medical records (representative of 47,783 hospital admissions) for the year 2009 was analyzed.


The main results found in this study were an incidence rate of 11.1% AEs, of which around 53.2% were considered preventable. The majority of AEs were associated with surgical procedures (27%), drug errors (18.3%) and hospital acquired infections (12.2%). Most AEs (61%) resulted in minimal or no physical impairment or disability, and 10.8% were associated with death. In 58.6% of the AEs’ cases, the length of stay was prolonged on average 10.7 days. Additional direct costs amounted to €470,380.00.


The magnitude of these results was critical, reinforcing the need of more detailed studies in this area. The knowledge of the incidence and nature of AEs that occur in hospitals should be seen as a first step towards the improvement of quality and safety in health care.

Patient safety; Medical errors; Hospitals; Quality of care; Adverse events