Which factors predict pulmonary hypertension in ILD?

Multiple risk factors for pulmonary hypertension such as age, sex, and weight, among others, do not appear to influence the severity of interstitial lung disease (ILD), according to a recent study presented at APSR 2023.

The lack of association between some markers and ILD severity indicated “the presence of alternative or additional contributing factors for pulmonary hypertension in patients with ILD,” said lead investigator Hui Li Ang from the Royal Melbourne Hospital in Victoria, Australia.

Ang and her team conducted a systematic review of eligible studies from the databases of Ovid Medline, Embase, and Central up to 31 May 2021. Studies were included if they were original research, had participants aged 18 years and above, patients with ILD of any aetiology, minimum sample size of 10 participants, and evaluated pulmonary hypertension using any diagnostic criteria.

A total of 33,111 records were identified from the search, of which 369 were primary articles and 36 secondary reports met the eligibility criteria. Additionally, 153 studies were included for risks and associations. Among the primary articles, 349 were observational studies, 12 randomized interventional studies, seven diagnostic accuracy studies, and one nonrandomized interventional study.

Ang and colleagues identified “easily obtainable clinical parameters that were consistently associated with the presence of pulmonary hypertension in ILD.” They observed positive associations between right heart catheterization (RHC) measurements for pulmonary hypertension and other noninvasive imaging measurements. [Ang HL, et al, APSR 2023]

On the other hand, there were no significant correlations seen with pulmonary hypertension in most studies reporting age, sex, weight, or body mass index, spirometry parameters, and the extent of lung fibrosis on computed tomography (CT).

Other risk factors, such as ILD subtypes, the GAP stage, and the composite physiological index, were only examined in single studies and required additional research.

Notably, “[t]he CT measurements of pulmonary artery size was positively correlated with mean pulmonary artery pressure on RHC in a few studies and could be a valuable adjunct for screening of pulmonary hypertension,” Ang said.

“Variables identified in this review may be used for risk stratification of pulmonary hypertension screening in combination with noninvasive tests,” she added.

Detection tool

In a recent study, however, US researchers developed a tool for the early detection of pulmonary hypertension in ILD, with a sensitivity of 86.5 percent, specificity of 86.3 percent, and area under the curve of 0.920 (p<0.001). A score of ≥6 on this detection tool correlated with a diagnosis of pulmonary hypertension in ILD. [Pulm Circ 2022;12:e12141]

“The … detection tool provides high sensitivity and specificity for detecting pulmonary hypertension in ILD patients,” the authors said. “With confirmation in larger cohorts, this tool could improve the diagnosis of pulmonary hypertension in ILD and may suggest further testing with RHC and earlier intervention with inhaled treprostinil and/or lung transplant evaluation.”

A common complication in patients with ILD, pulmonary hypertension may result in poor functional status, the need for supplemental oxygen, and worse outcomes. [Clin Chest Med 2013;34:695-705; Respir Med 2006;100:1734-1741; Eur Respir Rev 2013;22:292-301; Eur Respir J 2014;44:415-424; Respir Med 2018;139:72-78]