Rethinking the “Pan-Culture”: Clinical Impact of Respiratory Culturing in Patients With Low Pretest Probability of Ventilator-Associated Pneumonia

Abstract

Background Respiratory cultures are often obtained as part of a “pan-culture” in mechanically ventilated patients in response to new fevers or leukocytosis, despite an absence of clinical or radiographic evidence suggestive of pneumonia. Methods This was a propensity score-stratified cohort study of hospitalized mechanically-ventilated adult patients between 2014-2019, with new abnormal temperature or serum white blood cell count (NATW), but without radiographic evidence of pneumonia, change in ventilator requirements or documentation of purulent secretions. Two patient groups were compared: those with respiratory cultures performed within 36 hours following NATW, and those without respiratory cultures performed. The co-primary outcomes were the proportion of patients receiving >2 days of total antibiotic therapy and >2 days of broad-spectrum antibiotic therapy within 1 week following NATW. Results Of 534 included patients, 113 (21.2%) had respiratory cultures obtained and 421 (78.8%) did not. Patients with respiratory cultures performed were significantly more likely to receive antibiotics for >2 days within 1 week following NATW than those without respiratory cultures performed (total antibiotic adjusted odds ratio 2.57, 95% confidence interval 1.39-4.75; broad-spectrum antibiotic adjusted odds ratio 2.47, 95% confidence interval 1.46-4.20). Discussion Performance of respiratory cultures for fever/leukocytosis in mechanically-ventilated patients without increasing ventilator requirements, secretion burden or radiographic evidence of pneumonia was associated with increased antibiotic use within one week following incident abnormal temperature and/or WBC. Diagnostic stewardship interventions targeting performance of unnecessary respiratory cultures in mechanically-ventilated patients may reduce antibiotic overuse within intensive care units.

Fever and infections in surgical intensive care: an American Association for the Surgery of Trauma Critical Care Committee clinical consensus document

“…The widespread application of ‘pan-culture’ for fever has come into question as it is associated with increased antibiotic use without added clinical benefit and with significant harms, 18 including increased antibiotic use, costs, patient discomfort, and iatrogenic infections. 13 19 On the other hand, since the diagnostic accuracy of clinical exam alone is lacking (60% sensitive and 64% specific), we recommended that the clinical evaluation be supplemented with additional tests selectively guided by the clinical suspicion, patient symptomatology, and/or risk for certain infections.…”

“… 45 46 Respiratory cultures may help support the diagnosis, but the presence of bacteria on culture is not diagnostic of a pneumonia because a majority of intubated patients will have colonization of the endotracheal tube—this is especially true if tracheal aspirates are used, although the use of bronchioalveolar lavage (BAL) does not eliminate false positives or false negatives. 18 47 Unfortunately, a positive culture is often routinely managed with antibiotics regardless of the diagnostic impression. 25 48 …”

Leveraging diagnostic stewardship within antimicrobial stewardship programmes

“…The overreliance on respiratory culturing to diagnose VAP can be seen in the recent cohort study by Albin et al, who evaluated patients on mechanical ventilation with new abnormal white blood cell (WBC) count or temperature but without radiographic evidence, ventilatory changes or purulent secretion. 56 Amongst the 534 patients studied, 21.2% had respiratory tract sampling for microbial cultures. This respiratory tract culturing was strongly associated with prolonged unnecessary antimicrobial use (OR 2.32; 95% CI 1.23–4.24), including broad-spectrum antimicrobial use (OR 2.23; 95% CI 1.33–3.73).…”

A Survey of PICU Clinician Practices and Perceptions regarding Respiratory Cultures in the Evaluation of Ventilator-Associated Infections in the BrighT STAR Collaborative

“…Interestingly, HCWs from hospitals with the highest culture rates also viewed CDS less favorably. Single-center studies have identified similar themes of excessive endotracheal aspirate culturing including that clinicians or individual units have developed normalized "default" practices (24), have low thresholds to obtain cultures (29,30), have high vigilance for sepsis (26), and have fear of missing infection (24)(25)(26)31). These patterns align with psychologic factors relevant for clinical de-implementation, including difficulty breaking habits, and asymmetry of outcomes or loss aversion (e.g., clinician concern for missing a diagnosis feels stronger than the perception of harm from the intervention) (32).…”