Seropositive Antibodies Linked with Prevalence of Rheumatoid Arthritis-Associated ILD.

Samath Mathapathi, MD

A new study presented at the 14th Annual North American Young Rheumatology Investigator Forum (NYRIF 2020) found an association between seropositive rheumatoid factor (RF) or the presence of anti-cyclic citrullinated antibodies (ACPA) and an increased prevalence of interstitial lung disease (ILD) among patients with rheumatoid arthritis.

The retrospective case-control review, led by Samarth Mathapathi, MD, Resident at Scripps Green Hospital, examined various combinations of RF and ACPA serotypes among patients in order to determine associations with ILD prevalence. Furthermore, they compared selected outcomes to see whether seropositivity can help predict the course of rheumatoid arthritis ILD.

Mathapathi and team assessed a total of 2084 adult patients with rheumatoid arthritis with and without ILD. Of the total, 82 had ILD, and 2002 did not.

They excluded patients with other rheumatologic or pulmonary conditions.

Furthermore, the team defined RF positive (RF (+)) as RF >15 IU/mL, and ACPA positive (ACPA (+)) as ACPA >6 IU/mL.

In their analysis, patients were divided into groups according to RF and ACPA status. Then they compared ILD prevalence, pulmonary function tests, progression of CT/chest X-ray, average pulmonary artery pressures, home oxygen dependency, all-cause mortality, and hospitalization for respiratory failures rates among the cohorts.

Thus, the investigators noted that prevalence of ILD was 6.3% and 5.2% in the RF (+) / ACPA (+) and RF (+) / ACPA (-) groups, respectively (P = .534).

Prevalence was 3.9% in the RF (-) / ACPA (+) group and 1.3% in the RF (-) / ACPA (-) group (P < 0.05).

Furthermore, the mean titers of ACPA and RF in all ILD cohorts were 397 IU/mL and 484 IU/mL, respectively.

For those without ILD, means titers were 235 IU/mL for RF and 250 IU/mL for ACPA.

When compared across all the ILD groups, the outcomes among all other aforementioned measures were not significantly difference (P > .05).

The only notable exception was progression on imaging—which was significant only in the RF (+) / ACPA (-) group. Thus, the investigators believed that this finding suggests a potential difference in disease course or other confounding underlying conditions.

“Positive and higher titers of ACPA or RF may help predict development of RA-ILD but may not help prognosticate disease course,” they concluded.

They acknowledged that larger and prospective studies would be necessary to confirm and validate their findings.

Concomitant rheumatoid arthritis and ILD has a varying prevalence, ranging from 3.2-6.0 cases per 100,000. The median survival rate is 7.8 years. Notable risk factors include age, female sex, and severity of rheumatoid arthritis.

The study, “Comparison of Selected Outcomes in Seropositive vs. Seronegative Rheumatoid Arthritis-Associated Interstitial Lung Disease (RA-ILD),” was presented at NYRIF 2020.