This article is a narrative review that discusses the recommended sample size requirements to design a pilot study to assess the reliability of a questionnaire. A list of various sample size tables that are based on the kappa agreement test, intra-class correlation test and Cronbach’s alpha test has been compiled together. For all calculations, type I error (alpha) was set at a maximum value of 0.05, and power was set at a minimum value of 80.0%. For the kappa agreement test, intra-class correlation test, and Cronbach’s alpha test, the recommended minimum sample size requirement based on the ideal effect sizes shall be at least 15, 22, and 24 subjects respectively. By making allowances for a non-response rate of 20.0%, a minimum sample size of 30 respondents will be sufficient to assess the reliability of the questionnaire.The clear guideline of minimum sample size requirement for the pilot study to assess the reliability of a questionnaire is discussed and this will ease researchers in preparation for the pilot study. This study provides justification for a minimum requirement of a sample size of 30 respondents specifically to test the reliability of a questionnaire.

Background: Acute kidney injury (AKI) following cardiac surgery is well established but the reported incidence is variable due to varying definitions and criteria. Furthermore there is a paucity of such data from Southeast Asia. Objectives: To determine the incidence of AKI, the associated risk factors, and its impact on early mortality and intensive care unit/hospital stay. Method: This is a single centre retrospective observational study to evaluate outcomes on 1260 consecutive patients from a multi-ethnic Southeast Asian population who underwent a primary isolated coronary artery bypass graft (CABG) operation. Data was collected from the hospital’s electronic database and analysed using basic descriptive statistics and logistic regression. Results: Overall incidence was 36.2% including 5.5% of patients who required renal replacement therapy (RRT). Multivariate analysis identified age, insulin-dependent diabetes mellitus (IDDM), baseline serum creatinine level (SCr), recent myocardial infarction (MI), cardiopulmonary bypass (CPB) time and intra-aortic balloon pump (IABP) use as independent risk factors for AKI. For patients who required RRT, the SCr and IDDM remained independent predictors. Early 30-day mortality (11.5% vs 0.9%) was significantly higher in patients who developed AKI following CABG. Similarly, AKI was associated with a slight but statistically significant increase in intensive care unit (ICU) and hospital stay. Conclusion: Better prognostication and preventative strategies are required to better risk stratify patients undergoing CABG and optimise utilisation of limited healthcare resources.
Acute Kidney Injury