Since the outbreak of the COVID-19 epidemic, it has evolved continuously, and the contagiousness of different strains, the severity of post-infection, and the clinical outcome are all issues of great concern. Relevant biological marker studies are also emerging, but these markers are diverse, highly unknown, and complex mechanisms, and the predictors of case fatality and mortality vary in different studies in different countries.
For example, data from Belgium suggest that post-COVID-19 severity is associated with advanced age, renal insufficiency, elevated lactate dehydrogenase, thrombocytopenia, and obesity. Studies in China have shown that its severity is related to hematologic indicators such as advanced age, males, high body mass index, hypertension, low T lymphocyte and B lymphocyte counts. Among these different factors, age and weight appear to be independent risk factors for disease severity. However, awareness of these risk factors does not appear to have significantly reduced COVID-19 mortality.
The severity of COVID-19 infection in many populations is gender-related: men are more severe than women, and men have a higher mortality rate. There are two main theories for this phenomenon: (i) the theory of androgen drive; (ii) the theory of hypogonadism in men. Both theories involve hormone-related differences in the severity of diseases, so can sex hormone-related indicators be used as predictors of COVID-19 severity?
In March, the journal Scientific Reports published a new study in which scientists studied the proportion of length of four fingers (index, middle, ring, and little finger) in addition to the thumbs of covid-19-infected and healthy subjects, and explored their association with the severity of post-COVID-19 infection. The study found that a shorter ring finger length in men is a sign of lower testosterone, while the androgen testosterone is associated with the severity of post-COVID-19 infection, so the finger length ratio may be a predictor of severe COVID-19 infection and increased risk of hospitalization after infection with the virus.
The following information was recorded in the study protocol: disease severity (0-4 points; 0 points - asymptomatic, 1 point - mild, 2 points - moderate, 3 points - severe, 4 points - fatal), length of hospitalization and oxygen therapy, days in intensive care unit, concomitant disease, history of smoking and occupational exposure, laboratory test results (white blood cell count, fibrinogen, d-dimer, platelet count, oximetry, procalcitonin), and anthroporan measurements. The control group consisted of 47 women and 53 men, while the patient group consisted of 26 women and 28 men.
Based on the correlation between finger length ratios and case fatality rates (CFRs), the researchers concluded that compared to the control group, patients hospitalized for COVID-19 had:
(i) a higher ratio of left and right finger length, and a higher asymmetry of left and right directions of Δ, i.e., a history of exposure to low prenatal testosterone and high prenatal estrogen;
(ii) High | (right-left) | unsigned asymmetry (FA), i.e., elevated levels of developmental instability caused by stressors such as adolescent sex steroids.
Note: Index finger (2D), middle finger (3D), ring finger (4D), little finger (5D), patient (P), control (C). Average of 2D:3D, 2D:4D, 2D:5D, 3D:4D, 3D:5D, 4D:5D finger length ratio unsigned asymmetries (| right-left |). Clinical compound asymmetry (Comp-Asym) is calculated as | (| right-left). 2D: 4D + |right-left) | 3D:5D）/2。
There can be a considerable correlation between finger length ratios. For example, 2D:4D exhibits developmental stability, while 3D:5D is particularly unstable during development. Patterns associated with 2D:4D and 3D:5D are least likely to be affected by the interrelationship between finger length ratios. Thus, 2D:4D may be associated with prenatal-related factors, while 3D:5D may be associated with the postpartum effects of developmental instability. So the 2D:4D and 2D:4D finger length ratios should be of concern.
The study also examined the role of prenatal steroids and postpartum developmental instability in the COVID-19 course. The results suggest that the finger length ratio and its asymmetry can be used as a simple clinical marker of the potential risk of hospitalization due to COVID-19. For finger length ratios, the effects include all 5D finger length ratios, i.e. 2D:5D, 3D:5D, and 4D:5D (patient > control). For directional (left-right) asymmetry, there was no significant difference between patients and controls. The researchers say the unsigned composite asymmetry of 2D:4D and 3D:5D may help identify high-risk individuals hospitalized due to COVID-19.
Figure note: ROC curve of clinically complex asymmetric COVID-19 disease.
In summary, the study found that there was a difference in the proportion of finger length and symmetry between patients hospitalized due to COVID-19 and the control, and the patients had a higher level of developmental instability compared with the control, and the proportion of finger length involving the little finger should be focused on. The indicator "clinical compound asymmetry" may be useful for identifying individuals with high developmental instabilities and may therefore be used to distinguish individuals who are more severe after COVID-19 infection. However, to validate the prognostic value of clinical recommendations related to finger length ratios, further studies are needed based on large populations of different ethnic groups.
References:
1. Kasielska-Trojan, A., et al. "Digit ratios and their asymmetries as risk factors of developmental instability and hospitalization for COVID-19." Scientific Reports12.1 (2022): 1-10.
Written by | Latisha
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