Among patients with acute respiratory distress syndrome (ARDS), those who are also diagnosed with diffuse alveolar damage (DAD) via an open lung biopsy face nearly twice as high a mortality risk as did those without DAD, according to a systematic review and a meta-analysis by Dr. Pablo Cardinal-Fernandez and his colleagues.

The results of this and other studies “support the hypothesis that ARDS with DAD is a specific clinicopathological entity different from ARDS without DAD,” said Dr. Cardinal-Fernandez of the department of genetic medicine, Cornell University, New York, and his colleagues ( CHEST 2016 149:1155-64. ).

“Our meta-analysis underscores the need for less-invasive approaches to individualize therapy for patients with ARDS, including the development of biomarkers for predicting responses to treatments.”

The researchers analyzed studies identified using MEDLINE, EMBASE, Cochrane Register of Controlled Trials, LILACS, and citation review from Jan. 1, 1967, to Sept. 1, 2015. Eight studies involving 350 patients satisfied the researchers’ criteria for inclusion in the review. All of such studies included patients who received an open lung biopsy after being diagnosed with ARDS, histologic results indicating the presence or absence of DAD based on the open lung biopsy, and the mortalities of both a group of patients diagnosed with DAD and a group of patients not diagnosed with DAD. Studies were excluded from the review if they included fewer than five participants.

The pooled odds ratio for mortality in patients who had ARDS with DAD, compared with patients with ARDs who did not have DAD was 1.81.

At the time of ARDS diagnosis, the meta-differences for sequential organ failure assessment scores and the index of hypoxemia (PaO2/FiO2) ratio between the patients who had DAD and those who did not were 0.26 and 4.36, respectively. On the day of open lung biopsy, the meta-differences for the sequential organ failure assessment score and the PaO2/FiO2 ratio between the two patient groups were also small; the meta-difference for sequential organ failure was 0.45 and the meta-difference for the PaO2/FiO2 ratio was –8.63.

The higher mortality risk in the group of patients with DAD – despite patients in both groups having similar severities of illness – suggests that “the presence of DAD confers additional prognostic information,” according to the researchers.

“The mortality heterogeneity of this meta-analysis was low, suggesting that no other variables affect the results (that is, the observed effect depends mainly on the presence of DAD). Conditions that were identified in patients without DAD included pneumonia, pulmonary embolism, edema, or no pathologic abnormality. It appears that these subsets of patients have a different and better prognosis than did patients with ARDS and DAD, perhaps as a result of favorable responses to specific treatments, with the possible exception of lower tidal volume, which appears to be beneficial in all subgroups,” the researchers said.

No financial or nonfinancial disclosures were declared.