Microbiological ascertainment in patients with pneumonia: the experience of a teaching hospital in Rome.

Objectives: Pneumonia still remains a problem from the clinical and public health viewpoint because of the relevant epidemiological burden. The etiological diagnosis is important in the light of avoiding unnecessary antibiotic treatment and choosing the most appropriate therapeutical approach. This study is aimed at providing evidence on the proportion of microbiological ascertainment in pneumonia-related hospitalizations in one of the most important teaching hospitals in Rome.

Methods: The study relied on the record linkage of two administrative databases of the same hospital: the electronic hospital discharge register and the microbiology laboratory surveillance database.

Results: 2819 records were identified, where 46% had a microbiological ascertainment, significantly higher in males than in females (51% vs 40%) and in cases of pneumonia reported in secondary diagnosis instead of primary diagnosis (52% vs 42%). Medical patients had significantly lower proportion of ascertainment compared to surgical patients (43% vs 67%) whereas there were not differences between patients with emergency and elective admission. The overall mortality was 17%. Mortality was significantly higher: in surgical compared to medical patients (27% vs 15%), in ventilated compared to not ventilated patients (41% vs 11%), in cases with secondary diagnosis of pneumonia compared to a primary diagnosis (23% vs 11% ) and in hospitalized in intensive care unit-ICU- rather than in non-ICU (71% vs 12%).

Conclusion: The proportion of microbiological ascertaiment in pneumonia remains less than 50%. Albeit in line with other evidence, this result should call the attention on the impact of unknown etiological diagnosis on antibiotic treatment and resistance.