Value of the Pitt Bacteraemia Score to predict short-term mortality in Staphylococcus aureus bloodstream infection: a validation study
BACKGROUND AND AIMS
The widely used Pitt Bacteraemia Score (PBS) has repeatedly been described as a risk factor for short-term mortality in Staphylococcus aureus bloodstream infection (BSI), but little is known about its overall predictive performance. We therefore aimed to externally validate the PBS in S. aureus BSIs.
We performed a retrospective validation study at the University Hospital Basel. Adult patients with a first episode of methicillin-susceptible S. aureus BSI between January 2008 and December 2013 were eligible for the study. We measured the overall discriminative power of the PBS at day of BSI onset in predicting 30-day all-cause mortality by receiver-operating characteristics analysis. For each PBS cut-off, we calculated the corresponding sensitivity, specificity and predictive values for prediction of 30-day all-cause mortality.
A total of 329 patients were included in the final analysis: The median PBS at BSI onset was 0 (interquartile range, 0–2) with patients suffering from various comorbidities (Charlson Comorbidity Index median 3, interquartile range 1–5). Thirteen percent of patients (43/329) died within 30 days from any cause. At BSI onset, 52% (170/329) of patients had a PBS of zero; the concomitant specificity and positive predictive value for prediction of 30-day all-cause mortality were 0% and 13%, respectively. The overall performance of the PBS in predicting the 30-day all-cause mortality was lower than published, with an area under the curve of 0.711 (95% confidence interval 0.614–0.807; p <0.001).
For short-term mortality, the PBS had a low predictive value in a patient population with methicillin-susceptible S. aureus BSI. There is a need to improve simple clinical scores to better predict mortality, in particular for S. aureus.
- Laupland KB. Incidence of bloodstream infection: a review of population-based studies. Clin Microbiol Infect. 2013;19(6):492–500. doi:.https://doi.org/10.1111/1469-0691.12144
- López-Cortés LE, Del Toro MD, Gálvez-Acebal J, Bereciartua-Bastarrica E, Fariñas MC, Sanz-Franco M, et al.; REIPI/SAB group. Impact of an evidence-based bundle intervention in the quality-of-care management and outcome of Staphylococcus aureus bacteremia. Clin Infect Dis. 2013;57(9):1225–33. doi:.https://doi.org/10.1093/cid/cit499
- Skogberg K, Lyytikäinen O, Ollgren J, Nuorti JP, Ruutu P. Population-based burden of bloodstream infections in Finland. Clin Microbiol Infect. 2012;18(6):E170–6. doi:.https://doi.org/10.1111/j.1469-0691.2012.03845.x
- Korvick JA, Bryan CS, Farber B, Beam TR, Jr, Schenfeld L, Muder RR, et al. Prospective observational study of Klebsiella bacteremia in 230 patients: outcome for antibiotic combinations versus monotherapy. Antimicrob Agents Chemother. 1992;36(12):2639–44. doi:.https://doi.org/10.1128/AAC.36.12.2639
- Paterson DL, Ko WC, Von Gottberg A, Mohapatra S, Casellas JM, Goossens H, et al. International prospective study of Klebsiella pneumoniae bacteremia: implications of extended-spectrum beta-lactamase production in nosocomial Infections. Ann Intern Med. 2004;140(1):26–32. doi:.https://doi.org/10.7326/0003-4819-140-1-200401060-00008
- van Hal SJ, Jensen SO, Vaska VL, Espedido BA, Paterson DL, Gosbell IB. Predictors of mortality in Staphylococcus aureus bacteremia. Clin Microbiol Rev. 2012;25(2):362–86. doi:.https://doi.org/10.1128/CMR.05022-11
- Pedersen M, Benfield TL, Skinhoej P, Jensen AG. Haematogenous Staphylococcus aureus meningitis. A 10-year nationwide study of 96 consecutive cases. BMC Infect Dis. 2006;6(1):49. doi:.https://doi.org/10.1186/1471-2334-6-49
- Hill PC, Birch M, Chambers S, Drinkovic D, Ellis-Pegler RB, Everts R, et al. Prospective study of 424 cases of Staphylococcus aureus bacteraemia: determination of factors affecting incidence and mortality. Intern Med J. 2001;31(2):97–103. doi:.https://doi.org/10.1111/j.1444-0903.2001.00029.x
- Rhee JY, Kwon KT, Ki HK, Shin SY, Jung DS, Chung DR, et al. Scoring systems for prediction of mortality in patients with intensive care unit-acquired sepsis: a comparison of the Pitt bacteremia score and the Acute Physiology and Chronic Health Evaluation II scoring systems. Shock. 2009;31(2):146–50. doi:.https://doi.org/10.1097/SHK.0b013e318182f98f
- Al-Hasan MN, Lahr BD, Eckel-Passow JE, Baddour LM. Predictive scoring model of mortality in Gram-negative bloodstream infection. Clin Microbiol Infect. 2013;19(10):948–54. doi:.https://doi.org/10.1111/1469-0691.12085
- Al-Hasan MN, Juhn YJ, Bang DW, Yang HJ, Baddour LM. External validation of bloodstream infection mortality risk score in a population-based cohort. Clin Microbiol Infect. 2014;20(9):886–91. doi:.https://doi.org/10.1111/1469-0691.12607
- Osthoff M, Sidler JA, Lakatos B, Frei R, Dangel M, Weisser M, et al. Low-dose acetylsalicylic acid treatment and impact on short-term mortality in Staphylococcus aureus bloodstream infection: a propensity score-matched cohort study. Crit Care Med. 2016;44(4):773–81.
- Lemeshow S, Hosmer DW, Jr. A review of goodness of fit statistics for use in the development of logistic regression models. Am J Epidemiol. 1982;115(1):92–106. doi:.https://doi.org/10.1093/oxfordjournals.aje.a113284
- Liao CH, Chen SY, Huang YT, Hsueh PR. Outcome of patients with meticillin-resistant Staphylococcus aureus bacteraemia at an Emergency Department of a medical centre in Taiwan. Int J Antimicrob Agents. 2008;32(4):326–32. doi:.https://doi.org/10.1016/j.ijantimicag.2008.04.011