Clinical differences between Thai systemic sclerosis patients with positive versus negative anti-topoisomerase I.

BACKGROUND: Anti-topoisomerase I antibody (ATA) carries an increased risk of systemic sclerosis (SSc) internal organ involvement. There have been no published comparisons of the clinical characteristics of patients positive and negative for ATA in Thailand, where the positive rate for ATA is higher than among Caucasians.

OBJECTIVE: To define the clinical differences between SSc, positive versus negative, for ATA.

METHODS: A retrospective cohort study was performed among SSc patients over 18 at Srinagarind Hospital, Khon Kaen University, Thailand, during January 2006-December 2013. SSc-overlap syndrome was excluded.

RESULTS: Two hundred and ninety-four SSc patients were included (female : male 2.5 : 1). The majority (68.6%) were the diffuse cutaneous SSc subset (dcSSc). ATA was positive in 252 patients (85.7%), among whom 71.7% had dcSSc and 28.2% limited cutaneous SSc (lcSSc). Using a multivariate analysis, hand deformity had a significantly positive association with ATA (odds ratio [OR] 7.01; 95% CI 1.02-48.69), whereas being anti-centromere (ACA) positive had a negative association (OR 0.17; 95% CI 0.03-0.92). After doing a subgroup analysis of the SSc subset, the median duration of disease at time of pulmonary fibrosis detection among ATA positive dcSSc was significantly shorter than the ATA negative group (1.05 vs. 6.77 years, P = 0.01). Raynaud's phenomenon (RP) at onset was significantly more frequent in lcSSc sufferers who were ATA negative than those who were ATA positive (90.5% vs. 56.9%, P = 0.005).

CONCLUSIONS: A high prevalence of ATA positivity was found among Thai SSc patients and this was associated with a high frequency of hand deformity, ACA negativity, a short duration of pulmonary fibrosis in dcSSc and a lower frequency of RP in lcSSc.