Session Type: Poster Session (Tuesday)
Session Time: 9:00AM-11:00AM
Background/Purpose: Interstitial lung disease (ILD) is a critical comorbidity in RA. To manage RA-ILD, early diagnosis and monitoring disease progression are important. KL-6 is a marker of disease activity of ILD including CTD-ILD such as scleroderma. However, clinical values of KL-6 in the management of RA remain to be elucidated. The purpose of this study is to determine whether KL-6 elevation is useful to diagnose ILD, whether KL-6 elevation predicts newly developing/worsening ILD, and to whether KL-6 increase is associated with developing/worsening ILD.
Methods: A retrospective cohort study. Subjects were consecutive RA patients who started first biologic at Dokkyo Medical University Hospital and received HR-CT examination before and during biologics therapy and serum KL-6 levels were measured before the therapy. Medical records were reviewed retrospectively. Chest radiography was taken before biologics. When KL-6 levels were above 400 U/ml, KL-6 was judged as elevated. CT findings were accepted gold standard for the existence of ILD.
Results: Subjects were 129 patients, M/F; 44/85, mean age; 51.6year old, disease duration; 7.9 years, and RF-positivity; 83%. Chest radiography was taken in 107 cases. A sequential KL-6 examination was carried out in 86 cases. ILD was found in 48 patients (37%). At the entry, KL-6 levels were 468±239 U/ml in ILD group and 262±134 U/ml in non-ILD one (Fig.1). KL-6 elevation was found in 10/81 (11.3%) of non-ILD patients and in 23/48 (48%) of ILD ones.
The sensitivity, specificity, PPV and NPV of KL-6 to detect ILD were 0.47 0.70, 0.70 and 0.73, respectively, while the specificity, specificity, PPV and NPV of chest radiography were 0.6, 0.87, 0.67 and 0.65, respectively.
KL-6 at the entry failed to predict development/worsening of ILD. Newly emerging/ worsening ILD was found in 31/129 (24%) in whole. Newly emerging ILD was found similarly in 3/10 (30%) of patients with KL-6 elevation and 10/71 (14%) of those without elevation in non-ILD group (p=0.20). Worsening ILD was observed in 6/23 (26%) of patients with KL-6 elevation and 11/25 (44%) of those without the elevation in ILD group (p=0.23).
Increasing KL-6 levels during the observation period was associated with development/ worsening of ILD, which were observed in 23/50 (46%) of patients with KL-6 increase and 3/36 (8%) of those without the increase (p=0.0002). Similarly, development of ILD was found in 12/29 (41%) of non-ILD patients with KL-6 increase and 2/23 (9%) of those without the increase (P=0.009), and worsening of ILD was observed in 11/21 (52%) of ILD patients with KL-6 increase and 1/13(8%) of those without the increase (P=0.008).
Conclusion: KL-6 levels were increased in RA with ILD. However, KL-6 elevation was found in non-ILD patients, and there were ILD patients without KL-6 elevation. The ability of KL-6 to detect ILD is low like chest radiography. KL-6 elevation failed to predict development/worsening of ILD. However, the increase in KL-6 level is associated with development/worsening of ILD. Thus, KL-6 is a useful marker to monitor activity of ILD, but not to diagnose and predict it.
To cite this abstract in AMA style:Takamura Y, Tanaka A, Kurasawa K, Hasegawa A, Hiyama C, Miyao T, Yamazaki R, Arai S, Owada T, Maezawa R, Arima M. KL-6 Is a Useful Marker to Monitor the Progression of RA-ILD, but Not to Diagnose or Predict the Development of ILD [abstract]. Arthritis Rheumatol. 2019; 71 (suppl 10). https://acrabstracts.org/abstract/kl-6-is-a-useful-marker-to-monitor-the-progression-of-ra-ild-but-not-to-diagnose-or-predict-the-development-of-ild/. Accessed January 27, 2022.
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