Blood Profiling of Athletes after COVID-19: Differences in Blood Profiles of Post-COVID-19 Athletes Compared to Uninfected Athletic Individuals-An Exploratory Analysis

Abstract

Blood profiling data in athletic populations and their respective responses to SARS-CoV-2 infection are lacking. Thus, this exploratory pilot study aimed to analyze and compare clinical blood markers in previously infected trained athletes (ATH; 30 m/29 f) and a not previously infected healthy athletic control group (HC; 12 m/19 f). The ATH group undertook a sports medical examination which included extended blood analyses. Blood profiles with a total of 74 variables were assessed (blood counts, pro-/inflammatory and immunological markers, and micronutrients), and the ATH group was compared to the age-matched, vaccinated HC group with comparable athletic back grounds, though without previous SARS-CoV-2-infections. The ATH group showed lower IgG, Troponin-T levels, and they had a lower complement/acute-phase protein activation. Furthermore, Vitamin D levels were lower and electrolyte/micronutrient concentrations were higher in ATH. Soluble transferrin receptor as a marker of erythrocyte turnover was decreased whereas PTT as a coagulation marker was increased. Subgroup analyses according to sex revealed more differences between the women of the ATH and HC groups (for 25 different variables) than between the men (for 5 different variables), especially for immunological and metabolic variables. In particular, the immune system and electrolyte/micronutrient status should be observed frequently and sex-specifically in this athletic cohort.

Keywords: COVID-19; athletes; blood analysis; inflammation; long-term changes; physical activity; reference values; sex differences.

Figure 1

Blood cell system-specific differences between the previously COVID-19-infected athletes (ATH) and the healthy controls (HC) with comparable fitness statuses. Of the 27 variables grouped in the blood cell system, in the sub-group of white blood cells, significant differences for (A) leucocyte (HC 6.3 ± 1.0 vs. ATH 5.9 ± 1.5 ${10}^9$/L) and (B) absolute lymphocyte (HC 2.0 ± 0.4 vs. ATH 1.8 ± 0.5 ${10}^9$/L) concentrations were observed. In the sub-group of red blood cells, the specific variable (C) soluble transferrin receptor (HC 4.3 ± 1.7 vs. ATH 2.8 ± 0.6 mg/L) concentration was significantly different between the ATH and HC groups. * p ≤ 0.05 and **** p ≤ 0.0001 for the ATH group compared to the HC group.

Figure 2

Differences in the variables regarding immunology/inflammation (A–C) and complement system (D,E) between the previously infected athletes (ATH) and the healthy controls (HC) with comparable fitness statuses. Of the 17 variables grouped for inflammation/immunology, the (A) CRP (HC 1.3 ± 2.2 vs. ATH 0.6 ± 0.6 mg/L), (B) IgG (HC 12.0 ± 2.7 vs. ATH 10.5 ± 1.6 g/L), and (C) LBP (HC 5.0 ± 1.4 vs. ATH 4.1 ± 1.1 $\mathsf{\mu }$g/mL) concentrations were significantly different between the ATH and HC groups. The levels of (D) complement C3c (HC 1.1 ± 0.2 vs. ATH 1.0 ± 0.2 g/L) and (E) CH50 (HC 54.6 ± 4.4 vs. ATH 50.4 ± 5.9) and sub-grouped from immunology, differed between the ATH and HC groups. * p ≤ 0.05 and ** p ≤ 0.01 for the ATH group compared to the HC group.

Figure 3

Differences in the variables grouped for (A) coagulation, and (B) damage markers between the previously COVID-19-infected athletes (ATH) and the healthy controls (HC) with comparable fitness statuses. PTT (HC 28.3 ± 2.2 s vs. ATH 30.1 ± 3.2 s) was significantly different between the ATH and HC groups. Troponin-T concentrations in the ATH group (4.4 ± 4.1 ng/L) were significantly decreased compared to the HC group (7.4 ± 8.0 ng/L), whereas there were no differences for the other seven variables grouped as damage markers (e.g., creatine kinase, urea, and NT-Pro BNP). Of the six variables grouped under coagulation, * p ≤ 0.05, ** p ≤ 0.01.

Figure 4

Differences in the variables grouped under electrolytes/micronutrients between the previously COVID-19-infected athletes (ATH) and the healthy controls (HC) with comparable fitness statuses. Of the five variables grouped under electrolytes/micronutrients, (A) zinc (HC 11.7 ± 2.0 vs. ATH 12.4 ± 1.8 $\mathsf{\mu }$mol/L), (B) potassium (HC 3.9 ± 0.4 vs. ATH 4.3 ± 0.4 mmol/L), and (C) sodium (HC 139.7 ± 1.6 vs. ATH 140.3 ± 1.8 mmol/L) concentrations were significantly different between the ATH and HC groups. * p ≤ 0.05 and **** p ≤ 0.0001 for the ATH group compared to the HC group.

Figure 5

Differences in the variables grouped under metabolism between the previously COVID-19-infected athletes (ATH) and the healthy controls (HC) with comparable fitness sta-tuses. Of the elven variables grouped under metabolism, (A) ALT (HC 19.7 ± 8.1 vs. ATH 26.1 ± 13.6 U/L), (B) vitamin B6 (HC 108.4 ± 51.2 vs. ATH 165.3 ± 169.7 nmol/L), (C) TSH (HC 1.5 ± 0.6 vs. ATH 1.9 ± 0.8 mlU/L), (D) Triglyceride (HC 1.0 ± 0.6 vs. ATH 1.2 ± 0.6 mmol/L), (E) Protein (HC 76.0 ± 4.8 vs. ATH 73.4 ± 3.6 g/L) and (F) Vitamin D 25OH (HC 34.6 ± 9.9 vs. ATH 28.3 ± 14.2 $\mathsf{\mu }$g/L) concentrations were significantly different between the ATH and HC groups. * p ≤ 0.05, ** p ≤ 0.01 and *** p ≤ 0.001 for the ATH group compared to the HC group.