Levels of three vascular biomarkers – hepatocyte growth factor, soluble Flt-1, and platelet-derived growth factor – were elevated a mean of 3 years before systemic sclerosis (SSc) patients developed pulmonary hypertension (PH) in a prospective cohort of 300 subjects.
However, the associations with PH were not very robust. For instance, above an optimal cut point of 9.89 pg/mL for platelet-derived growth factor (PlGF), the sensitivity for future PH was 82%, specificity 56%, and area under the curve (AUC) 0.69. An elevation above the optimal cut point for soluble Flt-1 (sFlt1) – 93.8 pg/mL – was 71% specific and 51% sensitive, with an AUC of 0.61.
Adding PlGF and sFlt1 elevations to carbon monoxide diffusing capacity, N-terminal of the prohormone brain natriuretic peptide (NT-proBNP) level, and percent forced vital capacity to predict PH increased the AUC modestly, from 0.72 to 0.77.
The data suggest, perhaps, an early warning system for PH. “Once vascular biomarkers are observed to be elevated, the frequency of other screening tests (e.g., NT-proBNP, DLCO) may be increased in a more cost-effective approach,” wrote investigators led by rheumatologist Christopher Mecoli, MD, an assistant professor at Johns Hopkins University, Baltimore, in Arthritis & Rheumatology.
Dr. Daniel E. Furst
“In the end, the authors did not overstate the case and cautiously recommended that using biomarkers might be useful in the future. The finding that when there are increased numbers of abnormalities of vascular markers, there would be an increased probability of pulmonary hypertension, makes sense.” However, “this was a major fishing expedition, and the data are certainly not sufficient to suggest anything clinical but are of some interest with respect to the general hypothesis,” said rheumatologist Daniel Furst, MD, professor of medicine (emeritus) at the University of California, Los Angeles, when asked for comment.
The subjects were followed for at least 5 years and had no evidence of PH at study entry. Levels of P1GF, sFlt-1, hepatocyte growth factor (HGF), soluble endoglin, and endostatin were assessed at baseline and at regular intervals thereafter. A total of 46 patients (15%) developed PH after a mean of 3 years.
Risk of PH was associated with baseline elevations of HGF (hazard ratio, 1.99; 95% CI, 1.24-3.17; P = .004); sFlt1 (HR, 3.04; 95% CI, 1.29-7.14; P = .011); and PlGF (HR, 2.74; 95% CI, 1.32-5.69; P = .007).
Just 2 of 25 patients (8%) with no biomarkers elevated at baseline developed PH versus 12 of 29 (42%) with all five elevated. That translated to a dose-response relationship, with each additional elevated biomarker increasing the risk of PH by 78% (95% CI, 1.2-2.6; P = .004).
“There [was] no consistent trend of increasing biomarker levels over time as patients approach[ed] a diagnosis of [PH]. ... Serial testing may have value in patients with early disease to first detect elevations in biomarkers,” but “once elevated, the utility of serially monitoring appears low,” the investigators wrote.
It’s not surprising that “a higher number of elevated biomarkers relating to vascular dysfunction would correspond to a higher risk of PH,” the team wrote. However, “while these biomarkers hold promise in the risk stratification of SSc patients, many more vascular molecules exist which may have similar or greater value.”
There was no substantial correlation between any biomarker and disease duration, age at enrollment, or age at diagnosis, and no significant difference in biomarker level based on patient comorbidities. No biomarker was significantly associated with medication use at cohort entry, and none were significantly associated with the risk of ischemic digital lesions.
The majority of patients were white women. At enrollment, the average age was 52 years, and subjects had SSc for a mean of 10 years.
The work was funded by the National Institutes of Health, among others. Investigator disclosures were not reported.
SOURCE: Mecoli C et al. Arthritis Rheumatol. 2020 Mar 21. doi: 10.1002/art.41265.