Timeliness of microbiology test result reporting and association with outcomes of adults hospitalised with pneumonia: a data linkage study

Background: Pneumonia is one of the major causes of morbidity and mortality among young and elderly people across the globe. Microbiology tests play a critical role in the diagnosis of pneumonia. To date, the relationship between the time to first microbiology test result reporting and patient outcomes has not been reported in the existing literature. Objective: The objectives of this study are to determine: (1) microbiological test ordering patterns, (2) the timeliness of microbiological test reporting (e.g. the time from hospital admission to the first test result) and (3) associations of time to first microbiology test result reporting with patient outcomes (e.g. in-hospital mortality) among adult patients (aged ≥ 18 years) hospitalised with unspecified pneumonia. Method: A 3-year (2016-2018) retrospective cohort (data linkage) study in six hospitals in NSW, Australia. Study data were obtained by linking hospital and laboratory system databases. We used the International Classification of Diseases version 10-Australian Modification (ICD-10-AM) code J18.9 to identify patients hospitalised with unspecified pneumonia. Timeliness of result reporting indicators including the time from admission to the first and the last microbiology tests were determined. The outcome measures were hospital length of stay (LOS) and in-hospital mortality. We fit median and logistic regression to evaluate the association of time to first microbiology test result reporting with hospital LOS and in-hospital mortality respectively. Results: A total of 6,298 patients met the inclusion criteria. Of these, 85.3% (n=5,375) ordered at least one microbiology test. The top 5 microbiology tests were blood culture, urine culture, respiratory PCR, urine antigen and sputum culture. The median time to the first test result was 26 hrs (IQR, 13-58) while the median time to the last test was 144 hrs (IQR, 128-211). The rate of in-hospital mortality was 5.9% (n=371). After adjusting for confounders, every 5 hrs increase in the time-to first microbiology test was associated with an increase of 3.9 hrs in the median hospital LOS (95% CI, 3.5 to 4.3; P<0.001). There was no association between time to the first microbiology result and in-hospital mortality (OR 1.01; 95% CI 1.00-1.02; P=0.122).Conclusion: Time to first microbiology test result reporting was significantly associated with hospital LOS but not with in-hospital mortality. Further study should be conducted to understand if shortening time to first microbiology test result reporting can reduce the length of hospital stay of patients -- abstract.