MATERIAL AND METHODS
All patients under 15 years of age, hospitalized between 2010 and 2018 in the two study hospitals, with a primary or secondary diagnosis of pleural effusion or empyema were eligible. Exclusion criteria were: non-infectious cause of the effusion; tuberculosis; nosocomial pneumonia; unknown date of admission; patients transferred to finish their treatment in a center other than HA or HB; and patients with previous or concomitant severe comorbidities that could markedly interfere with the course, treatment or LOS, specifically patients with oncological diseases, immunodeficiencies, severe encephalopathies and myopathies, significant heart or lung diseases, or Down’s syndrome.
Medical records of the included patients were reviewed to register the date of admission and discharge, age, sex, previous diseases, days of fever, analytical and microbiological results in blood and pleural fluid, radiological characteristics of the effusion, and treatments used. The size of the effusion was considered a surrogate of severity and was classified according to the maximum thickness observed on imaging tests, as less than 10 mm (PPE/PE−) or 10 mm or more (PPE/PE+). Patients with PPE/PE+ were further divided into two groups according to the thickness of the effusion: 10 mm to 20 mm (PPE/PE+1) or greater than 20 mm (PPE/PE+2). The primary outcome measures were the proportion of patients undergoing pleural drainage and LOS. Total LOS was defined as the days between the patient’s first admission to a hospital with a diagnosis of PPE/PE until final discharge from the tertiary hospital. LOS in the tertiary reference hospital was defined as the days between admission to the reference hospital (from the emergency department or transferred from another center) and definitive discharge for this condition. In the case of patients who had been discharged from hospital but required a new admission for the same process, LOS included the days that the patient remained at home between the two hospitalizations. Other secondary variables were duration of fever and duration of intravenous antibiotic treatment.
The data collected were entered into a database for statistical analysis using the SPSS v.22 program. Statistical analyses were carried out using R software, version 4.0.2 (R Foundation for Statistical Computing, Vienna, Austria; http://www.R-project.org). Bilateral statistical tests were applied with a significance level set at 0.05. Normal distribution of the continuous variables was checked using the Kolmogorov-Smirnov test. Qualitative variables were described using frequencies and percentages, and quantitative variables using median and interquartile range, given that they were not normally distributed. To evaluate differences in the characteristics between two hospitals, we applied the Chi-square test or Fisher’s exact test (categorical variables) or the Mann-Whitney U test (continuous variables). The study was approved by the research ethics committees at HA and HB.