Background/Purpose:

Rheumatoid arthritis (RA) prevalence and clinical phenotype varies between ethnic groups. Few studies have analyzed differences in disease expression between Latin-Americans mestizos (LA) and Caucasians in a population with the same access to healthcare. The purpose of this study is to compare the activity, severity and prognostic factors, of RA in Spanish Caucasians and LA followed at the same Spanish health centre and with the same access to healthcare and antirheumatic therapy.

Methods:
Cross-sectional case-control study of RA patients (ACR 1987 criteria) aged 18-65 years attending a specialized RA clinic of a tertiary Spanish hospital between September 2011 and December 2012. For each LA patient, 2 Spanish Caucasians matched by disease duration (± 12 months) were selected. Sociodemographic variables, disease activity, prognostic markers, serology and treatment were collected and compared between the two groups.

Results:
Of a total of 314 patients with RA, a sample of 153 RA patients (51 LA and 102 Spanish Caucasians) were finally included. The mean age was 47.3 ± 10 years and 88% were female. Disease duration and age at disease onset was similar between groups. LA had  more active disease than Spanish Caucasians as measured by DAS28, number of tender and swollen joints, patient global health assessment or ESR (see table). Remission or low disease activity defined by DAS28 was achieved less frequently by LA patients (15.7% vs. 40.2%, p=0.002, OR 3.61, 95% CI: 1.54 – 8.47 and 31.3% vs. 56.8%, p=0.003, OR 2.88, 95% CI: 1.42- 5.86, respectively). Disability measured by mHAQ and erosive disease were similar in the two groups. There were no significant  differences in the treatment received between groups, although LA patients more frequently received glucocorticoids, synthetic DMARDs and biologic therapy. LA patients more frequently had seropositive RA (rheumatoid factor and/or anti-CCP positive) and were less frequently current and past smokers. Other factors that may be related to disease activity, such as obesity and vitamin D deficiency, were significantly more frequent in LA patients.

Conclusion:
Latin-American mestizo patients had differing prognostic factors and more active RA than Spanish Caucasian patients, despite having the same access to health care and receiving similar antirheumatic therapy.

Table. Disease activity and disability in Caucasian and Latin American  patients with RA.

	Total n=153	Caucasian n=102	Latin American n=51	p
Age at diagnosis	40.11 ± 11.84	40.54 ± 12.04	39.24 ± 11.51	0.523
Disease duration (months)	91.25 ± 93.03	91.13 ± 92.94	91.5 ± 94.14	0.982
Disease duration < 2 years %	33.98%	22.55%	23.53%	0.892
Age at inclusion	47.30 ± 10.59	47.76 ± 10.73	46.37 ± 10.34	0.554
Sex % (female)	88.2%	87.25%	90.2%	0.595
Obesity (BMI > 25)	57.7%	50%	72.92%	0.009
Smoker	51.4%	63.27%	27.08%	0.000
Anti-CCP+	84.1%	80%	92.57%	0.053
RF +	71.1%	65.35%	82.35%	0.029
TJC	3.42 ± 5.02	2.36 ± 3.38	5.53 ± 6.84	0.003
SJC	2.72 ± 3.91	2.29 ± 3.33	3.57 ± 4.8	0.057
PGH	37.71 ± 19.31	34.41 ± 17.89	44.31 ± 20.52	0.003
DAS28	3.5 ± 1.46	3.16 ± 1.33	4.17 ± 1.49	0.000
Remission DAS28 < 2.6 %	32%	40.2%	15.7%	0.002
Low disease activity DAS28 < 3.2 %	48.4%	56.86%	31.37%	0.003
Pain VAS	34.75 ± 26.97	30.16 ± 21.64	44.74 ± 34.24	0.027
mHAQ	0.374 ± 0.474	0.373 ± 0.45	0.371 ± 0.52	0.986
CRP	0.82 ± 1.22	0.73 ± 1.2	1.01 ± 1.26	0.173
ESR	21.52 ± 19.16	19.44 ± 19.89	25.71 ± 17.01	0.056
Hemoglobin	129.60 ± 12.93	132.04 ± 11.81	124.68 ± 13.65	0.001
Glucocorticosteroids %	52.9%	48.04%	62.75%	0.086
DMARDs %	82.2%	81.2%	86.75%	0.355
Biologic therapy %	38.2%	36.63%	41.18%	0.586
Erosions %	51.9%	51.09%	53.49%	0.795
Vitamin D	19.78 ± 10.75	21.69 ± 10.64	15.88 ± 9.98	0.003

BMI: body mas index, RF: rheumatoid factor, TJC: tender joint count, SJC: swollen joint count, PGH: patient global health asessment, DAS: disease activity index, VAS: visual analogue scale, mHAQ: modified health asnessment quiestionnarie, CRP: C reactive protein, ESR: erythrocyte sedimentation rate, DMARDs: disease-modifying anti-rheumatid drugs.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/differing-disease-expression-in-latin-american-mestizo-and-spanish-caucasian-patients-with-rheumatoid-arthritis-with-the-same-access-to-healthcare-and-antirheumatic-treatment/