Characteristics of the study population
The study population included 266 participants, of them 166 (63.1%) were females [mean age 41.4 ± 15.5 years] and 97 (36.9%) were males [mean age 36.2 ± 16.0 years]. The study participants overall, aged between 1 and 85 years with average of 40 years. The participants were classified into 85 (31.2%) cases and 181 (68.8%) were controls. Based on age grouping, the age groups of 21–40 years followed by 41–60 years were the most frequent age groups; with 106 (39.8%) and 101 (38.0%) participants, respectively. Whereas, the frequency of the remaining age groups was 35 (13.2%) for 1–20 years, 23 (8.6%) for 61–80 years, and 1 (0.4%) for the age group of more than 80 years.
Among the studied population, those were from Arab ethnicity were the most frequent; 109 (41.0%). Also, those with a previous history of RA were 27 (10.2%), whereas those with no family history constituted 239 (89.8%). Based on duration of RA among the case group, the most frequent age group was 41–60 years; 53 (62.3%). And the duration of RA among the case group included 42 (49.4%) were having RA for less than 5 years, 29 (34.1%) for 5–10 years, and 7 (8.2%) for each of 11–15 years and 15–20 years (Table 1).
Table 1
| Age Groups | Total | P value |
20-Jan | 21–40 | 41–60 years | 61–80 years | More than 80 years |
years | years |
Gender |
Male | 14 (40.0%) | 50 (47.2%) | 25 (24.8%) | 8 (34.8%) | 0 (0.0%) | 97 (36.5%) | 0.017 |
Female | 21 (60.05) | 56 (52.8%) | 76 (75.2%) | 15 (65.2%) | 1 (100%) | 169 (63.5%) |
Total | 35 (13.2%) | 106 (39.8%) | 101 (38.0%) | 23 (8.6%) | 1 (0.4%) | 266 (100%) |
Ethnic |
Arab | 10 (28.6%) | 39 (36.8%) | 51 (50.5%) | 9 (39.1%) | 0 (0.0%) | 109 (41.0%) | 0.006 |
Beja | 4 (11.4%) | 21 (19.8%) | 23 (22.8%) | 2 (8.7%) | 0 (0.0%) | 50 (18.8%) |
Fur | 18 (51.4%) | 26 (24.5%) | 15 (14.9%) | 9 (39.1%) | 1 (100%) | 69 (25.9%) |
Nuba | 2 (5.7%) | 9 (8.5%) | 9 (8.9%) | 0 (0.0%) | 0 (0.0%) | 20 (7.5%) |
Nubian | 1 (2.9%) | 11 (10.4%) | 3 (3.0%) | 3 (13.0%) | 0 (0.0%) | 18 (6.8%) |
Total | 35 (13.2%) | 106 (39.8%) | 101 (38.0%) | 23 (8.6%) | 1 (0.4%) | 266 (100%) |
Participant status |
Case | 1 (2.9%) | 18 (17.0%) | 53 (52.3%) | 13 (56.5%) | 0 (0.0%) | 85 (32.0%) | 0.001 |
Control | 34 (97.1%) | 88 (83.0%) | 48 (47.5%) | 10 (43.5%) | 1 (100%) | 181 (68.0%) |
Total | 35 (13.2%) | 106 (39.8%) | 101 (38.0%) | 23 (8.6%) | 1 (0.4%) | 266 (100%) |
Family history of RA |
Yes | 0 (0.0%) | 5 (4.7%) | 18 (17.8%) | 4 (17.4%) | 0 (0.0%) | 27 (10.2%) | 0.004 |
No | 35 (100%) | 101 (95.3%) | 83 (82.2%) | 19 (82.6%) | 1 (100%) | 239 (89.8%) |
Total | 35 (13.2%) | 106 (39.8%) | 101 (38.0%) | 23 (8.6%) | 1 (0.4%) | 266 (100%) |
Duration of RA |
less than 5 years | 1 (100%) | 10 (55.6%) | 27 (50.9%) | 4 (30.8%) | 0 (0.0%) | 42 (49.4%) | 0.672 |
5–10 years | 0 (0.0%) | 6 (33.3%) | 16 (30.2%) | 7 (53.8%) | 0 (0.0%) | 29 (34.1%) |
11–15 years | 0 (0.0%) | 1 (5.6%) | 6 (11.3%) | 0 (0.0%) | 0 (0.0%) | 7 (8.2%) |
15–20 years | 0 (0.0%) | 1 (5.6%) | 4 (7.5%) | 2 (15.4%) | 0 (0.0%) | 7 (8.2%) |
Total | 1 (1.2%) | 18 (21.2%) | 53 (62.3%) | 13 (15.3%) | 0 (0.0%) | 85 (100%) |
Prevalence of IL-17A genotypes in the study population
The distribution of the different IL-17A genotypes among the study population was 52.6% (140/266) AG heterozygote genotype, 38.4% (102/266) AA homozygote genotype, and 9.0% (24/266) GG homozygote genotype. The heterozygote AG genotype was most frequent among those aged 41–60 years; 63 (45.0%), followed by 50 (35.7%) among 21–40 years. While the homozygote AA genotype was most frequent among 21–40 years followed by 41–60 years; 46 (45.1%) and 27 (26.5%), respectively. Whereas, the homozygote GG genotype was frequent among 11 (45.8%) of the age group 41–60 years followed by 10 (41.7%) of the age group 21–40 years. A statistically significant difference was noted for the distribution of the different IL-17A genotypes among the different age groups, P value 0.022.
Based on the different ethnic groups of the study population, the homozygote AA genotype was more frequent among Fur; 31 (30.4%), while the homozygote GG genotype was more frequent among Arab; 13 (54.2%). Whereas, heterozygote AG genotype was among Arab ethnicity; 68 (48.6%). The distribution of the different IL-17A genotypes among the different ethnic groups was statistically significant, P value 0.034.
Regarding the family history and duration of RA, the heterozygote AG genotype was found among 23 (16.4%) of those with family history of RA, as well as those with duration of RA for less than 5 years; 36/85 (55.4%). However, a statistically significant difference was noted for the distribution of the different IL-17A genotypes according to family history, no statistically significant difference was seen fort the distribution of IL-17A genotypes according to duration of RA, p values 0.001 and 0.321, respectively (Table 2).
Table 2
| IL17Genotype | Total | P value |
AA | GG | AG |
Age Group |
1–20 years | 22 (21.6%) | 1 (4.2%) | 12 (8.6%) | 35 (13.2%) | 0.022 |
21–40 years | 46 (45.1%) | 10 (41.7%) | 50 (35.7%) | 106 (39.8%) |
41–60 years | 27 (26.5%) | 11 (45.8%) | 63 (45.0%) | 101 (38.0%) |
61–80 years | 7 (6.9%) | 2 (8.3%) | 14 (10.0%) | 23 (8.6%) |
More than 80 years | 0 (0.0%) | 0 (0.0%) | 1 (0.7%) | 1 (0.4%) |
Total | 102 (38.4%) | 24 (9.0%) | 140 (52.6%) | 266 (100%) |
Ethnic |
Arab | 28 (27.5%) | 13 (54.2%) | 68 (48.6%) | 109 (41.0%) | 0.034 |
Beja | 27 (26.5%) | 2 (8.3%) | 21 (15.0%) | 50 (18.8%) |
Fur | 31 (30.4%) | 4 (16.7%) | 34 (24.3%) | 69 (25.9%) |
Nuba | 9 (8.8%) | 3 (12.5%) | 8 (5.7%) | 20 (7.5%) |
Nubian | 7 (6.9%) | 2 (8.3%) | 9 (6.4%) | 18 (6.8%) |
Total | 102 (38.4%) | 24 (9.0%) | 140 (52.6%) | 266 (100%) |
Family History of RA |
Yes | 2 (2.0%) | 2 (8.3%) | 23 (16.4%) | 27 (10.2%) | 0.001 |
No | 100 (98.0%) | 22 (91.7%) | 117 (83.6%) | 239 (89.8%) |
Total | 102 (38.4%) | 24 (9.0%) | 140 (52.6%) | 266 (100%) |
Duration of RA |
less than 5 years | 2 (28.6%) | 4 (30.8%) | 36 (55.4%) | 42 (49.4%) | 0.321 |
5–10 years | 3 (42.9%) | 7 (53.8%) | 19 (29.2%) | 29 (34.1%) |
11–15 years | 1 (14.3%) | 2 (15.4%) | 4 (6.2%) | 7 (8.2%) |
15–20 years | 1 (14.3%) | 0 (0.0%) | 6 (9.2%) | 7 (8.2%) |
Total | 7 (8.2%) | 13 (15.3%) | 65 (76.5%) | 85 (100%) |
Correlation of IL-17A genotypes with gender, family history of RA, and clinical status of the study participant
The correlation of the different IL-17A genotypes was negatively statistically significant based on participants clinical status; case and control, and family history of RA, Pearson’s correlation [r = -0.392, p-value 0.001] and [r = -0.226, p-value 0.001], respectively. While correlation of IL-17A genotypes was positively statistically significant with participant gender, Pearson’s correlation [r = 0.140, p-value 0.023]. Whereas based on the duration of RA, no statistically significant correlation was observed, Pearson’s correlation [r = -0.138, p-value 0.207] (Table 3).
Table 3
| IL17 Genotypes | M ± STD | Pearson's r | P value | 95% Confidence Interval |
AA | GG | AG | Lower Bound | Upper Bound |
Participant status |
Case | 7 (6.9%) | 13 (54.2%) | 65 (46.4%) | 1.68 ± 0.467 | -0.392 | 0.001 | 1.62 | 1.74 |
Control | 95 (93.1%) | 11 (45.8%) | 75 (53.6%) |
Gender |
Male | 47 (46.1%) | 6 (25.0%) | 44 (31.4%) | 1.64 ± 0.482 | 0.14 | 0.023 | 1.58 | 1.69 |
Female | 55 (53.9%) | 18 (75.0%) | 96 (68.6%) |
Family History |
Yes | 2 (2.0%) | 2 (8.3%) | 23 (16.4%) | 1.9 ± 0.303 | -0.226 | 0.001 | 1.86 | 1.94 |
No | 100 (98.0%) | 22 (91.7%) | 117 (83.6%) |
Duration of RA |
less than 5 years | 2 (28.6%) | 4 (30.8%) | 36 (55.4%) | 2.75 ± 0.925 | -0.138 | 0.207 | 2.55 | 2.95 |
5–10 years | 3 (42.9%) | 7 (53.8%) | 19 (29.2%) |
11–15 years | 1 (14.3%) | 2 (15.4%) | 4 (6.2%) |
15–20 years | 1 (14.3%) | 0 (0.0%) | 6 (9.2%) |