Background/Purpose:

Rheumatoid arthritis (RA) has a myriad of pulmonary manifestations and RA-associated interstitial lung disease (RA-ILD) causes the most clinical concern. Subclinical ILD may be identified in up to 60% of individuals with RA, and lung disease is responsible for 10-20% of overall deaths and 80% of deaths in those with clinically significant lung disease.   Known risk factors for RA lung disease include smoking and male gender.  In this study, we sought to describe a large cohort of RA-ILD evaluated at our center.

Methods:

We identified all subjects with a diagnosis of RA and ILD at our center between January 1987 and June 2012 (N=350).  All subjects were confirmed to have RA by their treating rheumatologist.   Patients without a high resolution computed tomography (HRCT) or surgical lung biopsy were excluded.  The final cohort consisted of 135 subjects.  All data were extracted from comprehensive medical review.  Kaplan Meier survival analysis was performed on those with usual interstitial pneumonia (UIP) and non-specific interstitial pneumonia (NSIP).

Results:

Tables 1 displays the cohort characteristics as a whole and Table 2 displays the comparison of those with UIP and NSIP.  There was no significant difference among those with UIP (median 100.3 months) compared to NSIP (median 58.3 months) (p=0.5). 

Table 1 – Baseline Demographics and Pulmonary Function Tests

Age at Initial Visit	63 (21 to 90)
Gender (%male)	42%
Current or Past Smokers	67%
RF Positivity	79%
RF Level	822 (0 to 13300)
CCP Positivity	76%
CCP Level	134 (0 to 323)
ANA positivity	14%
%FEV1	67% (22 to 113%)
%FVC	66% (30 to 122%)
%TLC	84% (45 to 143%)
%DLCO	70% (31 to 127%
ILD Subtypes
Usual Interstitial Pneumonia	31% (43)
Nonspecific Interstitial Pneumonia	30% (41)
Fibrosis NOS	12% (17)
Cyyptogenic Organizing Pneumonia	2% (3)
Other	22.5% (31)

Table 2 – Usual Interstitial Pneumonia vs Nonspecific Pneumonia

	Usual Interstitial Pneumonia	Nonspecific Interstitial Pneumonia
Age at initial visit	63 (39-84)	62 (26-84)
Gender (% male)	70%	22%
Past or current smokers	63%	60%
RF positivity	100%	76%
CCP positivity	83%	68%
%FVC	59% (30-100%)	67% (32-112%)
%DLCO	62% (39-96%)	75% (31-111%)
%TLC	76% (53-105%)	80% (45-128%)

Conclusion:

In contrast to prior studies that suggest UIP is the most common pattern in RA-ILD, equal numbers of subjects with UIP and NSIP were identified in our large cohort.  We also found a significant number of subjects in whom lung disease was either too mild to classify or had fibrotic features both of NSIP and UIP (28% of our cohort).  Furthermore, in contrast to prior studies that suggest RA-UIP has worse survival than RA-NSIP, underlying histologic pattern did not impact survival in our cohort.   Prospective studies are needed to further understand the impact of histopathology on the natural history of RA-ILD.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rheumatoid-arthritis-associated-interstitial-lung-disease-clinical-spectrum-of-a-large-cohort-from-a-respiratory-referral-center/