The alveolar-arterial gradient, pneumonia severity scores and inflammatory markers to predict 30-day mortality in pneumonia

Abstract

Objective: The objective of this study was to evaluate the association of elevated alveolar-arterial oxygen (A-a O₂) gradient with risk of mortality in hospitalized patients with community-acquired pneumonia (CAP).

Methods: This prospective study included 206 patients diagnosed with CAP admitted to the ED. Demographics, comorbidities, arterial blood gas, serum electrolytes, liver-renal functions, complete blood count, NLR, PLR, CRP, CAR, procalcitonin, A-a O₂ gradient, expected A-a O₂ and A-a O₂ difference were evaluated. PSI and CURB-65 scores were classified as follow: a) PSI low risk (I-III) and moderate-high risk (IV-V) groups; b) CURB-65; low risk (0-2) and high risk (3-5) groups.

Results: The survival rates of the PSI class (I-III) were significantly higher than the ones of the PSI class (IV-V) (92.1% vs. 62.9%, respectively). The percentage of survivors of the CURB-65 score (0-2) group (81.9%) was higher than the survivors of CURB-65 score (3-5) group (27.8%). Creatinine, BUN, uric acid, phosphorus, RDW, CRP, CAR, procalcitonin, lactate, A-a 0₂ gradient, expected A-a 0₂ and A-a 0₂ difference were significantly higher and basophil was lower in non-survivors. A-a O₂ gradient (AUC 0.78), A-a O₂ difference (AUC 0.74) and albumin (AUC 0.80) showed highest 30-day mortality prediction. NLR (AUC 0.58) and PLR (AUC 0.55) showed lowest 30-day mortality estimation. Procalcitonin (AUC 0.65), PSI class (AUC 0.81) and PSI score (AUC 0.86) indicated statistically significant higher 30-day mortality prediction.

Conclusion: A-a O₂ gradient, A-a O₂ difference and albumin are potent predictors of 30-day mortality in CAP patients in the ED.

Keywords: Alveolar-arterial oxygen gradient; Community-acquired pneumonia; Mortality.