Development of a respiratory severity score for hospitalized adults in a high HIV-prevalence setting—South Africa, 2010-2011

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Authors

Millman, Alexander J.
Greenbaum, Adena
Walaza, Sibongile
Cohen, Adam L.
Groome, Michelle J.
Reed, Carrie
McMorrow, Meredith
Tempia, Stefano
Venter, Marietjie
Treurnicht, Florette K.

Journal Title

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BioMed Central

Abstract

BACKGROUND : Acute lower respiratory tract infections (LRTI) are a frequent cause of hospitalization and mortality in South Africa; however, existing respiratory severity scores may underestimate mortality risk in HIV-infected adults in resource limited settings. A simple predictive clinical score for low-resource settings could aid healthcare providers in the management of patients hospitalized with LRTI. METHODS : We analyzed 1,356 LRTI hospitalizations in adults aged ≥18 years enrolled in Severe Acute Respiratory Illness (SARI) surveillance in three South African hospitals from January 2010 to December 2011. Using demographic and clinical data at admission, we evaluated potential risk factors for in-hospital mortality. We evaluated three existing respiratory severity scores, CURB-65, CRB-65, and Classification Tree Analysis (CTA) Score assessing for discrimination and calibration. We then developed a new respiratory severity score using a multivariable logistic regression model for in-hospital mortality and assigned points to risk factors based on the coefficients in the multivariable model. Finally we evaluated the model statistically using bootstrap resampling techniques. RESULTS : Of the 1,356 patients hospitalized with LRTI, 101 (7.4%) died while hospitalized. The CURB-65, CRB-65, and CTA scores had poor calibration and demonstrated low discrimination with c-statistics of 0.594, 0.548, and 0.569 respectively. Significant risk factors for in-hospital mortality included age ≥ 45 years (A), confusion on admission (C), HIV-infection (H), and serum blood urea nitrogen >7 mmol/L (U), which were used to create the seven-point ACHU clinical predictor score. In-hospital mortality, stratified by ACHU score was: score ≤1, 2.4%, score 2, 6.4%, score 3, 11. 9%, and score ≥ 4, 29.3%. Final models showed good discrimination (c-statistic 0.789) and calibration (chi-square 1.6, Hosmer-Lemeshow goodness-of-fit p-value = 0.904) and discriminated well in the bootstrap sample (average optimism of 0.003). CONCLUSIONS : Existing clinical predictive scores underestimated mortality in a low resource setting with a high HIV burden. The ACHU score incorporates a simple set a risk factors that can accurately stratify patients ≥18 years of age with LRTI by in-hospital mortality risk. This score can quantify in-hospital mortality risk in an HIV-endemic, resource-limited setting with limited clinical information and if used to facilitate timely treatment may improve clinical outcomes.

Description

Additional file 1: BMC Pulmonary_Severity Score Data.xlsx. Severity Score Dataset. Dataset generated and used for analysis and creation of the ACHU score. Two tabs are included 1) includes the data used for the analysis 2) includes important notes related to the analytical methods and definitions for several composite variables.
Additional file 2: Table S1. CURB-65, CRB-65, Classification Tree Analysis (CTA) severity scores. Table S2. Predicted and observed risk of mortality based on CURB-65, CRB-65, Classification Tree Analysis (CTA), and CURB-45 severity scores among hospitalized adults with lower respiratory tract infections, South Africa, 2010–2011. Table S3. Predicted and observed risk of mortality based by ACHU (Age, confusion, HIV, urea) respiratory severity score among hospitalized adults with lower respiratory tract infections, South Africa, 2010–2011.

Keywords

Patients, Hospitalization, Mortality, Lower respiratory tract infection (LRTI), Severe acute respiratory illness (SARI)

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Citation

Millman, AJ, Greenbaum, A, Walaza, S, Cohen, AL, Groome, MJ, Reed, C, McMorrow, M, Tempia, S, Venter, M, Treurnicht, FK, Madhi, SA, Cohen, C & Variava, E 2017, 'Development of a respiratory severity score for hospitalized adults in a high HIV-prevalence setting—South Africa, 2010-2011', BMC Pulmonary Medicine, vol. 17, art. no. 28, pp. 1-8.