Diagnostic accuracy of Gram staining when predicting staphylococcal hospital-acquired pneumonia and ventilator-associated pneumonia: a systematic review and meta-analysis.

Abstract (298/300) Background There is no clear guidance on empiric antibiotic coverage against Staphylococcus aureus (S. aureus) for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). Objectives To evaluate if the presence of clusters of Gram-positive cocci in Gram staining of respiratory samples predicts S. aureus as HAP/VAP pathogen. Data sources MEDLINE, PubMed, Embase, Scielo, CINAHL and Scopus, from inception to 15/07/2017 (update on 31/10/2019) and original data from a single-centre database (PROSPERO: CRD42017072138). Study eligibility criteria We included studies reporting the diagnostic accuracy of a Gram staining evaluation suggestive of Staphylococcus compared with a positive culture for S. aureus in any type of lower respiratory tract sample. Participants Adult patients with HAP/VAP. Index test Morphological evaluation of Gram staining of respiratory samples. Methods We followed PRISMA guidelines and assessed risk of bias and applicability with the QUADAS-2 tool. We conducted a meta-analysis using a bivariate random effects model. Results We selected five studies that included only VAP and data from a single-centre database including VAP and HAP. We pooled six studies for VAP and analysed 1,665 respiratory samples. Pooled sensitivity was 68% (95% CI, 49-83%) and specificity, 95% (95% CI, 86-98). The pooled positive likelihood ratio was 12.7 (95% CI, 5.1-31.6); negative likelihood ratio, 0.34 (95% CI, 0.20-0.57); diagnostic odds ratio, 38 (95% CI, 13-106) and area under the SROC, 0.91 (95% CI, 0.88-0.93). There was great heterogeneity between sensitivity and specificity. In scenarios, in which prevalence of S. aureus was between 5 and 20%, the positive and negative predictive values were 62% (95% CI, 47-77%) and 95% (95% CI, 82-100%), respectively. Conclusions Gram-positive cocci in clusters in respiratory samples of patients with VAP has potential to guide risk assessments of S. aureus for more personalised antibiotic coverage. Randomised clinical trials with patient-centred outcomes are needed for strong clinical recommendations.