Effect of Formal Education Level on Measurement of Rheumatoid Arthritis Disease Activity

Hyeon Su Kim; Ui Hong Jung; Hyesun Lee; Seong-Kyu Kim; Hwajeong Lee; Jung-Yoon Choe; Sang Gyu Kwak; Theodore Pincus; Sung-Hoon Park

doi:10.4078/jrd.2015.22.4.231

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Kim, Jung, Lee, Kim, Lee, Choe, Kwak, Pincus, and Park: Effect of Formal Education Level on Measurement of Rheumatoid Arthritis Disease Activity

Original Article

J Rheum Dis 2015;22(4):231-237.

Published online: 31 October 2015

DOI: https://doi.org/10.4078/jrd.2015.22.4.231

Effect of Formal Education Level on Measurement of Rheumatoid Arthritis Disease Activity

Hyeon Su Kim¹, Ui Hong Jung¹, Hyesun Lee¹, Seong-Kyu Kim¹, Hwajeong Lee¹, Jung-Yoon Choe¹, Sang Gyu Kwak², Theodore Pincus³, Sung-Hoon Park¹

¹Department of Internal Medicine, Catholic University of Daegu School of Medicine, Daegu, Korea

²Department of Medical Statistics, Catholic University of Daegu School of Medicine, Daegu, Korea

³Division of Rheumatology, Rush University School of Medicine, Chicago, IL, USA

Corresponding to: Sung-Hoon Park, Department of Internal Medicine, Catholic University of Daegu School of Medicine, 33 Duryugongwon-ro 17-gil, Nam-gu, Daegu 42472, Korea. E-mail: yourii99@cu.ac.kr

Received 30 April 2015 Revised 4 June 2015 Accepted 4 June 2015

This is a Free Access article, which permits unrestricted non-commerical use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective

The aim of this study is to analyze the capacity of three demographic variables – age, sex, and formal education level – as well as disease duration to explain variation in 7 Core Data Set variables and 4 indices used to assess rheumatoid arthritis (RA), in a cohort of Korean patients seen in usual care.

Methods

All RA Core Data Set measures were collected in usual care of 397 RA patients, including tender/swollen joint counts (TJC, SJC) 28, physician global estimate of status, erythrocyte sedimentation rate, C-reactive protein, and a multidimensional health assessment questionnaire to assess physical function, pain, and patient global estimate of status (PATGL). Four indices were computed: disease activity score with 28 joint count (DAS28), simplified disease activity index (SDAI), clinical disease activity index (CDAI), and routine assessment of patient index data 3 (RAPID3). Descriptive statistics and multivariate generalized linear models were used in data analysis.

Results

Patients with lower education had higher scores, indicating greater severity, for all 7 Core Data Set measures and 4 indices (significant for TJC, function, pain, PATGL, DAS28, SDAI, CDAI, RAPID3). In a series of regressions that included age, sex, disease duration, and education, formal education level was the only significant variable to explain variation in TJC, pain, PATGL, physician global estimate of status (DOCGL), DAS28, SDAI, CDAI, and RAPID3.

Conclusion

Significant associations with education were found in Korean RA patients according to most RA Core Data Set measures and 4 indices. Education was more likely than age, sex, or disease duration to explain variation in most measures and indices.

Keywords: Rheumatoid arthritis, Social class, Education

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Table 1.

Demographic and clinical parameters of study population

Parameter	Female	Male	Total
Number of patients	355 (89.4)	42 (10.6)	397 (100)
Age (yr)	54.8 (46.2∼61.7)	60.0 (45.8∼64.2)	55.3 (46.2∼62.1)
Disease duration (yr)	7.3 (3.2∼13.8)	5.5 (2.1∼7.8)	6.8 (3.1∼13.4)
BMI (kg/m²)	22.1 (20.2∼24.3)	21.8 (20.8∼24.1)	22.0 (20.2∼24.3)
MDHAQ physical function	1.0 (0.3∼2.7)	1.3 (0.7∼2.3)	1.0 (0.3∼2.7)
MDHAQ pain	4.0 (2.0∼6.0)	4.5 (2.5∼7.0)	4.0 (2.0∼6.5)
PATGL	5.0 (2.5∼6.0)	5.0 (3.5∼7.0)	5.0 (3.0∼6.0)
DOCGL	3.0 (2.0∼4.0)	3.0 (2.0∼4.0)	3.0 (2.0∼4.0)
ESR (mm/h)	25.0 (15.0∼42.0)	21.0 (12.0∼36.0)	24.0 (15.0∼41.0)
CRP (mg/dL)	0.2 (0.1∼0.7)	0.3 (0.1∼0.9)	0.2 (0.1∼0.7)
RF (IU/mL)	39.1 (16.4∼85.9)	37.6 (18.4∼173.8)	38.6 (16.5∼88.7)
ACPA (U/mL)	115.5 (14.5∼500.0)	106.5 (50.5∼500.0)	107.3 (15.5∼500.0)
RAPID3	10.3 (5.7∼14.7)	11.0 (7.2∼16.0)	10.5 (6.0∼14.7)
DAS28	3.5 (2.7∼4.5)	3.6 (2.7∼4.6)	3.5 (2.7∼4.5)

Values are presented as number (%) or median (interquartile range). ACPA: anti-citrullinated protein antibodies, BMI: body mass index, CRP: C-reactive protein, RF: rheumatoid factor, DAS28: disease activity score with 28 joint count, DOCGL: physician global estimate of status, ESR: erythrocyte sedimentation rate, MDHAQ: multidimensional health assessment questionnaire, PATGL: patient global estimate of status, RAPID3: routine assessment of patient index data 3.

Table 2.

Rheumatoid arthritis measures and indices according to years of formal education

Measure/index	Formal education			p-value*
Measure/index	Elementary n=76 (19.1%)	High school n=228 (57.4%)	College n=93 (23.5%)	p-value*
Age (yr)	62.9 (0.8)	55.8 (0.6)	42.9 (1.1)	＜0.001
Female (%)	93	89	87	0.396†
Disease duration (yr)	7.0 (1.0)	7.6 (0.5)	5.1 (0.7)	0.084
TJC28 (0∼28)	2.5 (0.6)	1.0 (0.3)	1.0 (0.4)	0.003
SJC28 (0∼28)	0.0 (0.2)	0.0 (0.1)	0.0 (0.2)	0.125
MDHAQ physical function (0∼10)	2.0 (0.2)	1.0 (0.1)	1.0 (0.1)	＜0.001
MDHAQ pain (0∼10)	5.0 (0.3)	4.0 (0.2)	3.5 (0.2)	＜0.001
PATGL (0∼10)	5.0 (0.3)	5.0 (0.2)	4.5 (0.3)	0.046
DOCGL (0∼10)	3.0 (0.2)	2.0 (0.1)	3.0 (0.2)	0.071
ESR (mm/h, normal ＜30 mm/h)	28.0 (2.5)	23.0 (1.5)	28.0 (2.1)	0.292
CRP (mg/dL, normal ≤0.5 mg/dL)	0.2 (0.1)	0.2 (0.1)	0.3 (0.1)	0.598
RF (IU/mL, normal ≤15 IU/mL)	34.8 (8.7)	40.1 (4.7)	33.5 (6.5)	0.796
ACPA (U/mL, normal ≤17 U/mL)	101.9 (25.3)	100.0 (14.4)	173.2 (22.5)	0.263
DAS28	4.0 (0.1)	3.4 (0.1)	3.3 (0.1)	0.001
SDAI	13.3 (0.9)	9.5 (0.5)	10.5 (0.3)	0.003
CDAI	13.0 (0.9)	9.0 (0.5)	8.5 (0.7)	0.002
RAPID3	12.3 (0.7)	10.0 (0.4)	9.3 (0.6)	＜0.001

Values are presented as median (standard error). Elementary school: ＜7 years, high school: 7∼12 years, college: ＞12 years. ACPA: anti-citrullinated protein antibodies, CDAI: clinical disease activity index, CRP: C-reactive protein, DAS28: disease activity score with 28 joint count, DOCGL: physician global estimate of status, ESR: erythrocyte sedimentation rate, MDHAQ: multidimensional health assessment questionnaire, PATGL: patient global estimate of status, RAPID3: routine assessment of patient index data 3, RF: rheumatoid factor, SDAI: simplified disease activity index, SJC28: 28 swollen joint count, TJC28: 28 tender joint count.

^* p-value by Kruskal-Wallis test except where otherwise indicated;

^† Pearson's chi-square test.

Table 3.

Comparisons of American College of Rheumatology Core Data Set measures among patients grouped according to years of formal education

Dependent variable	Generalized linear model*			Pairwise comparisons
	F	p-value	R²	Elementary∼ high school		Elementary school∼ college		High school∼ college
	F	p-value	R²	Estimate (SE)	p-value	Estimate (SE)	p-value	Estimate (SE)	p-value
TJC28	2.40	0.036	0.029	1.6 (0.6)	0.006	1.7 (0.8)	0.021	0.2 (0.5)	0.749
SJC28	0.88	0.495	0.011	0.4 (0.2)	0.103	0.5 (0.3)	0.137	0.1 (0.2)	0.730
MDHAQ physical function	5.26	＜0.001	0.063	0.7 (0.2)	0.001	0.8 (0.3)	0.007	0.1 (0.2)	0.766
MDHAQ pain	4.18	0.001	0.050	1.4 (0.4)	＜0.001	1.7 (0.5)	＜0.001	0.4 (0.3)	0.298
PATGL	1.89	0.095	0.023	0.8 (0.3)	0.022	1.1 (0.4)	0.011	0.4 (0.3)	0.269
DOCGL	2.38	0.038	0.029	0.6 (0.2)	0.008	0.7 (0.3)	0.019	0.1 (0.2)	0.665
ESR	2.70	0.020	0.033	4.8 (3.0)	0.118	4.4 (4.0)	0.276	−0.4 (2.9)	0.896
CRP	0.68	0.641	0.008	−0.1 (0.2)	0.605	0.2 (0.3)	0.466	0.4 (0.2)	0.126

^* Performed after adjusting for age, sex and disease duration. CRP: C-reactive protein, DOCGL: physician global estimate of status, ESR: erythrocyte sedimentation rate, F: observed F value, MDHAQ: multidimensional health assessment questionnaire, PATGL: patient global estimate of status, R²: coefficient of determination, SE: standard error, SJC28: swollen 28 joint count, TJC28: tender 28 joint count.

Table 4.

Comparison of composite rheumatoid arthritis indices among patients grouped according to years of formal education

Dependent variable	Generalized linear model*			Pairwise comparisons
	F	p-value	R²	Elementary∼ high school		Elementary school∼ college		High school∼ college
	F	p-value	R²	Estimate (SE)	p-value	Estimate (SE)	p-value	Estimate (SE)	p-value
DAS28	3.91	0.001	0.047	0.6 (0.2)	＜0.001	0.6 (0.2)	0.005	0.0 (0.2)	0.881
SDAI	2.48	0.031	0.030	3.2 (1.1)	0.003	4.2 (1.4)	0.003	1.1 (1.0)	0.302
CDAI	2.81	0.016	0.034	3.3 (1.0)	0.001	4.0 (1.3)	0.002	0.7 (1.0)	0.463
RAPID3	4.09	0.001	0.049	2.9 (0.8)	＜0.001	3.7 (1.1)	＜0.001	0.8 (0.8)	0.311

^* Performed after adjusting for age, sex and disease duration. CDAI: clinical disease activity index, DAS28: disease activity score with 28 joint count, F: observed F value, R²: coefficient of determination, RAPID3: routine assessment of patient index data 3, SDAI: simplified disease activity index, SE: standard error.

Table 5.

Multiple linear regressions to analyze each American College of Rheumatology Core Data Set measure and 4 composite rheumatoid arthritis indices as dependent variables

Dependent variable	Independent variable: β coefficient (p-value)				R²
Dependent variable	Age	Sex	Disease duration	Education	R²
TJC28	0.000 (0.999)	0.475 (0.483)	0.289 (0.292)	−0.130 (0.034)	0.019
SJC28	−0.009 (0.331)	−0.004 (0.989)	0.130 (0.239)	−0.021 (0.430)	0.002
MDHAQ physical function	0.016 (0.097)	0.129 (0.633)	0.012 (0.256)	−0.051 (0.053)	0.043
MDHAQ pain	−0.008 (0.621)	0.559 (0.196)	−0.001 (0.957)	−0.140 (0.001)	0.038
PATGL	−0.017 (0.232)	0.681 (0.091)	0.011 (0.505)	−0.016 (0.007)	0.023
DOCGL	−0.018 (0.048)	0.259 (0.300)	−0.014 (0.163)	−0.072 (0.003)	0.027
ESR	−0.206 (0.109)	1.351 (0.709)	0.504 (0.001)	−0.539 (0.123)	0.004
CRP	−0.010 (0.341)	0.272 (0.346)	0.001 (0.917)	−0.027 (0.326)	0.005
DAS28	−0.010 (0.153)	0.181 (0.363)	0.021 (0.009)	−0.059 (0.002)	0.022
SDAI	−0.054 (0.231)	1.684 (0.184)	0.040 (0.436)	−0.365 (0.003)	0.025
CDAI	−0.044 (0.294)	1.411 (0.233)	0.039 (0.418)	−0.337 (0.003)	0.025
RAPID3	−0.009 (0.798)	1.369 (0.156)	0.022 (0.567)	−0.297 (0.002)	0.038

CDAI: clinical disease activity index, CRP: C-reactive protein, DAS28: disease activity score with 28 joint count, DOCGL: physician global estimate of status, ESR: erythrocyte sedimentation rate, MDHAQ: multidimensional health assessment questionnaire, PATGL: patient global estimate of status, R²: coefficient of determination, RAPID3: routine assessment of patient index data 3, SDAI: simplified disease activity index, SJC28: 28 swollen joint count, TJC28: 28 tender joint count.

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