Can the Second to Fourth Digit Ratio (2D : 4D) Be a Marker to Determine Ankylosing Spondylitis Disease Activity?

Abstract

Objective. The length ratio of the index finger (2D) to the ring finger (4D) (2D : 4D ratio) is considered a biomarker of prenatal sex hormone exposure. The 2D : 4D ratio is influenced by prenatal androgen and estrogen levels. Because ankylosing spondylitis (AS) influences men more frequently and severely than women, androgens are proposed to be related to AS pathogenesis. Estrogens have immune-modulating effects and reduce AS disease activity. The aim of this study was to assess the relationship between 2D : 4D ratio and AS disease activity. Material and Methods. In this study, 167 (43 female) patients diagnosed with AS were studied. The lengths of the second and fourth fingers were measured using a digital caliper. The 2D : 4D ratio was found by dividing the length of the second finger by the length of the fourth finger. AS disease activity was assessed with the Turkish version of the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). AS functional status was assessed with Bath Ankylosing Spondylitis Functional Index (BASFI). L-Schober, tragus to wall distance, finger to floor distance, and chest expansion were used to evaluate mobility. Results. In female patients, the right hand 2D : 4D ratios were higher than those in male patients. Biologic drug use was more frequent in males. The BASDAI scores were higher in female patients than in male patients. There were significant negative correlations between right and left hand 2D : 4D ratio and BASFI and BASDAI in female patients. There was no significant correlation between the 2D : 4D ratio and BASFI or BASDAI in male patients. We found a positive correlation between L-Schober and right hand 2D : 4D and a negative correlation between the left hand 2D : 4D ratio and finger to floor distance in female patients with AS. Conclusion. The 2D : 4D ratio of the right and left hand was low in female patients with high BASFI and BASDAI and low spinal mobility (L-Schober) was also linked to low female 2D : 4D. The lack of strong associations between 2D : 4D and AS in male patients may have resulted from their higher use of biologics.

Reviewing Disease Activity Indices in Spondyloarthritis From the Sex Perspective: A Systematic Review and Metaanalysis

“…Nearly all the studies (n = 38, 92.7%) were published in or after 2010, with 26 of them (63.4%) in or after 2015. According to the study design, 31 studies (75.6%) were cross-sectional, 14,24,[27][28][29][31][32][33][34][35][36][37][38]40,41,[44][45][46][47][48][49][53][54][55][56][57][58][59][60][61][62] 9 studies (22.0%) were cohort studies, 15,25,30,39,42,43,[50][51][52] and 1 was a case-control study. 26 Twenty-five studies (61.0%) included patients with AS, 15,25,26,[30][31][32][33][36][37]…”

“…All participants fulfilled SpA classification criteria, excluding 2 studies 32,40 that used general disease classification plus rheumatologic assessment, and 2 studies that did not identify their criteria. 28,44 Regarding the patients source, 21 studies (51.2%) included primary data or records from rheumatology departments, [24][25][26][27]29,31,33,35,36,38,39,41,45,47,49,50,54,55,58,59,60 8 studies (26.7%) included rheumatology patients from prospective cohorts, 14,15,42,43,51,52,56,62 6 studies included rheumatology patients from registries, 30,32,34,40,48,53 4 studies included patients from associations, 28,37,44,57 1 study included patients from the Bulgarian population, 46 and 1 cross-sectional study pooled 4 randomized controlled trials (RCTs). 61 The studies involved participants from 36 different countries, and most studies (80.5%) inc...…”

“…Quality assessment. Out of a maximum of 9 on the NOS, 11 studies were rated as 5, 41,44,46,48,49,51,54,55,57,58,60 10 studies as 6, 15,25,28,29,32,34,45,47,52,61 8 studies as 7, 14,24,26,30,36,38,40,50 and 12 studies as 8 27,31,33,35,37,39,42,43,53,56,59,62 (Supplementary Table 2, available with the online version of this article). In the selection section, all studies met at least half the items on the NOS, with the loss of initially eligible subjects being the main concern.…”

“…Women had higher BASDAI than men (Figure 3), which was similar to the findings in the fixed-effect model (0.53 [95% CI 0.47-0.60], P < 0.00001). Twenty-four 14,15,[27][28][29][30][32][33][34][35][36][37][38]40,44,48,52,53,55,56,[59][60][61][62] of the 41 studies showed higher disease activity in women than men, and 17 studies [24][25][26]31,39,[41][42][43][45][46][47][49][50][51]54,57,58 did not detect sex-related differences. The Q test identified heterogeneity (P = 0.002), which was quantified as moderate (I 2 = 44%) according to Deeks, et al 23 Regarding publication bias, the funnel plot (Figure 4) did not suggest any asymmetries, in accordance with the Egger test that did not detect publication bias (P = 0.17).…”

Is there a correlation between the second to fourth digit ratio and vitiligo? A cross‐sectional study

“…Many studies have suggested a link between the 2D:4D ratio and various diseases, including acne vulgaris 20,21 , seborrheic dermatitis 22 , psoriasis 23 , androgenetic alopecia 24 , thyroid disease 25 , lupus erythematosus 26 , multiple sclerosis 27 , ankylosing spondylitis 28 , some psychiatric disorders 29 , and some cancers (such as prostate and bladder) 30,31 . However, to our knowledge, there is not and published research on vitiligo and digit ratio.…”