Alveolar–arterial Oxygen Gradient, Pneumonia Severity Index and Outcomes in Patients Hospitalized With Community Acquired Pneumonia

Abstract

The alveolar-arterial oxygen gradient (DeltaA-a) provides a useful assessment of ventilation/perfusion (V/Q) abnormalities. The objectives of the present study were to: (i) examine the correlation between the DeltaA-a and the pneumonia severity index (PSI); and (ii) determine whether these measures were comparable in predicting clinical outcomes. The present study was conducted at a 750-bed teaching hospital. It examined a retrospective cohort of 255 patients with community acquired pneumonia (CAP) over a 2 year period. Association between the CAP and DeltaA-a was investigated by regression models and correlation, as well as two logistic models for subjects bifurcated by low-risk/moderate-to-high risk. The decision levels (DL) for both PSI and DeltaA-a were then compared as predictors of both length of stay (LOS) and survival. The correlation between PSI and DeltaA-a was strong (rho = 0.76; P < 0.0001) and was best modelled by a curvilinear relationship. Both logistic models indicated a strong association (P < 0.001) between DeltaA-a and PSI and yielded an optimal DL for the DeltaA-a of < 89 mmHg. Inter-test agreement of DeltaA-a with PSI was 76.9% (kappa = 0.60; 95% confidence interval 0.47-0.72; P < 0.0001). At < 89 mmHg, the odds ratios for LOS were similar to those at PSI = 90 in predicting LOS in the range 3-7 days, inclusive. There was no significant difference in the ability of DeltaA-a and PSI to predict survival for either the low- or high-risk group (P = 0.363 and P = 0.951, respectively). The DeltaA-a correlates well with PSI and performs comparably in predicting two major outcomes in subjects hospitalized with CAP.

Cardiac Troponin I Levels and Alveolar-arterial Oxygen Gradient in Patients with Community-acquired Pneumonia

“…Fisher's exact test was used to evaluate statistical significance of dichotomised categorical data and the odds ratio (OR) was used to evaluate the magnitude of effect. The cut-off previously established [7] for high-risk CAP (≥89 mmHg) was used to dichotomise this variable; receiver-operating characteristic (ROC) curve analysis was used to establish a cut-off for cTnI. For statistical evaluation, α was set at 0.05; p-values (two-sided) < 0.05 were considered statistically significant.…”

“…The dynamic range of this assay is 0.01-100 ng/ml, however samples may be further diluted to estimate concentrations 10-fold higher. The values for A-a were calculated as previously described [7].…”

“…In this study, we examined levels of cTnI, a widely utilised marker of myocardial damage as a potential index of severity in CAP. Having previously demonstrated that A-a at Table 1 a decision level of 89 mmHg is a useful surrogate for PSI to distinguish lower-risk cases from higher risk cases of CAP [7], we examined the association of cTnI with A-a in a retrospectively developed cohort of patients with CAP. The data presented herein demonstrate a significant association of cTnI with A-a.…”

“…We have shown that the ventilation-perfusion (V-Q) mismatch, as described by the alveolar-arterial O 2 gradient ( A-a), is strongly associated with the PSI and appears to be equivalent to the PSI in predicting clinical outcomes [7]. Thus, it might be expected that the V-Q abnormality reflected by increased A-a would lead to increased cTnI.…”

Guidelines for diagnosis and management of community-and hospital-acquired pneumonia in adults: Joint ICS/NCCP(I) recommendations

“…[112] Hence, CURB-65 can be supplemented with clinical judgment and/or pulse oximetry. [113–117] In a meta-analysis of 397,875 patients, CRB-65 performed well in stratifying the severity of pneumonia and the resultant 30-day mortality in hospital settings, while it appeared to overpredict the probability of 30-day mortality across all strata of predicted risk in community settings. [118] CRB-65 had an acceptable ability to classify mortality risk in the age group >65 years; patients with CRB-65 ≤1 had a relatively small mortality rate, which suggested that they could be managed as outpatients.…”