The level of purine metabolism metabolites in blood plasma, depending on the length of underground experience of coal miners, is shown in Figure 1.
Comparative analysis of purine metabolism metabolites group levels in blood plasma depending on the length of underground experience of coal miners (Figure 1) using the Kruskal-Wallis test showed that statistically significant differences were found in guanine (p=0.001), hypoxanthine (p=0.009), adenine (p=0.001) and xanthine (p=0.003). The level of uric acid (p=0.089) did not reach such values. However, the general trend remains - a decrease with an experience of up to 3 years and a subsequent significant increase with an experience of more than 5 years. Finding statistically significant differences, pairwise comparisons of uric acid levels were made between 1st and 3d groups, 1st and 4th groups, 2nd and 3d groups, 2nd and 4th groups using the Mann-Whitney test (Table 1).
Table 1. Pairwise comparative analysis of uric acid values in experienced groups using the Mann-Whitney test.
Groups
|
Value
|
Average rank
|
Mann-Whitney statistic (U)
|
Z
|
P*
|
2 group
|
Uric acid
|
25.57
|
302
|
-1.738
|
0.082
|
3 group
|
34.59
|
2 group
|
Uric acid
|
25.03
|
286.0
|
-2.343
|
0.019**
|
4 group
|
36.77
|
1 group
|
Uric acid
|
26.98
|
344.5
|
-1.076
|
0.282
|
3 group
|
33.12
|
1 group
|
Uric acid
|
26.23
|
322
|
-2.082
|
0.037**
|
4 group
|
35.61
|
* Significance level р=0.05
** - Statistically significant level р
|
As Table 1 shows, statistically significant changes in uric acid ranks were found between groups 2 and 4 (p=0.019), 1 and 4 (p=0.037).
Median values of purine metabolism indicators (adenine, guanine, hypoxanthine, xanthine and uric acid) depending on the age of coal miners are presented in Table 2.
Table 2. Values of purine metabolism depend on the age of coal miners (Me (Q25; Q75))
Value МЕ (Q1; Q3)
|
Age
|
х2
|
df
|
P*
|
Under 30 years old
|
From 30 to 40 years old
|
For over 40 years old
|
Guanine
|
161
(124; 187)
|
159
(120.5; 221)
|
169,5
(137.25; 220)
|
3.252
|
2
|
0.197
|
Hypoxanthine
|
131
(105; 154)
|
134 (100; 177)
|
143
(113.25; 181)
|
1.276
|
2
|
0.528
|
Adenine
|
105 (88; 119)
|
111
(83; 143.5)
|
122,5
(100.25;147)
|
3.252
|
2
|
0.197
|
Xanthine
|
164
(128; 178)
|
156
(125; 208.5)
|
164,5
(134.75; 207)
|
1.276
|
2
|
0.528
|
Uric acid
|
184
(131; 216)
|
165
(124.5;231)
|
177
(133; 221)
|
0.193
|
2
|
0.908
|
* Significance level р=0.05
|
The median values of guanine, hypoxanthine, and adenine are slightly higher in the age group over 40 years, and the values of xanthine and uric acid have opposite indicators in the three age groups. Intergroup comparisons using the Kruskal-Wallis index did not reveal statistically significant changes depending on the age of coal miners.
Xanthine oxidase activity assay inexperienced groups of coal miners were carried out in terms of the ratio of xanthine/hypoxanthine, uric acid/xanthine, uric acid/hypoxanthine. The xanthine/hypoxanthine ratio was calculated to assess hypoxia (Table 3).
Table 3. Values of xanthine oxidase activity and hypoxia in experienced groups of coal miners (Me (Q25; Q75))
Values
|
Experienced groups
|
х2
|
df
|
P
|
0 group
|
1st group
|
2nd group
|
3d group
|
4th group
|
Xan/HXN
1 stage XO
|
1.04
(0.9;1.13)
|
1.15 (1.09;1.28)
|
1.15 (1.04;1.27)
|
1.08 (0.98;1.16)
|
1.1
(1.02;1.18)
|
2.092
|
4
|
0.719
|
UA/Xan
2 stage XO
|
1.29 (1.19;1.4)
|
1.19 (1.1;1.29)
|
1.37 (1.45;1.67)
|
1.35 (0.07;1.44)
|
1.32 (1.18;1.43)
|
8.272
|
4
|
0.082
|
UA/HXN common stage XO
|
1.18(1.10;1.27)
|
1.15 (1.09;1.28)
|
1.17 (1.12;1.36)
|
1.20
(1.15;1.25)
|
1.19 (1.14;1.23)
|
2.092
|
4
|
0.719
|
Xan/G
|
0.97 (0.93;1.28)
|
0.99 (0.93;1.04)
|
0.97 (0.92;1.1)
|
1
(0.93;1.03)
|
0.97 (0.94;1.01)
|
1.612
|
4
|
0.807
|
* Significance level р=0.0127
Notice: Xan- xanthine, HXN – hypoxanthine, UA – uric acid, G- guanine, XO - xanthine oxidase
|
As can be seen from the presented table, statistical significance using the Kruskal-Wallis value was not achieved in experienced groups and the group of coal miners who do not have underground experience. Considering that in the uric acid/xanthine group p was the lowest but did not reach static significance, pairwise comparisons were made in experienced groups of coal miners using the Mann-Whitney U test (Table 4).
Table 4. Pairwise comparative analysis of uric acid/xanthine values in experienced groups of coal miners using the Mann-Whitney test
Groups
|
Mann-Whitney statistic (U)
|
Z
|
P*
|
Uric acid/Xanthine
|
0 group
|
414.5
|
-1.805
|
0.071
|
2 group
|
2 group
|
457.5
|
-2.301
|
0.021**
|
3 group
|
1 group
|
597.5
|
-0.935
|
0.350
|
2 group
|
0 group
|
449.5
|
-1.683
|
0.920
|
1 group
|
2 group
|
486.0
|
-1.297
|
0.195
|
4 group
|
* Significance level р=0.05
** - Statistically significant level р
|
Statistically significant differences were found only in terms of uric acid/xanthine between the 2nd and 3d groups. Thus, during the underground experience of 3 to 5 years, the activity of xanthine oxidase increases, catalyzing the oxidation of xanthine to uric acid and then decreases.
The activity of xanthine oxidase and the level of hypoxia do not depend on the age of coal miners (Table 5).
Table 5. Xanthine oxidase activity and hypoxia depend on the age of coal miners (Me (Q25; Q75))
Value МЕ (Q1; Q3)
|
Age
|
х2
|
df
|
P*
|
Under 30 years old
|
From 30 to 40 years old
|
For over 40 years old
|
Xan/HXN
|
1.21
(1.13; 1.29)
|
1.19
(1.11; 1.27)
|
1.2
(1.15;1.25)
|
0.589
|
2
|
0.745
|
UA/Xan
|
1.13
(1.04; 1.22)
|
1.11
(0.98; 1.19)
|
1.04
(0.97; 1.14)
|
0.946
|
2
|
0.623
|
UA/HXN
|
1.4 (1.22; 1.53)
|
1.35
(1.13; 1.47)
|
1.28
(1.14; 1.41)
|
3.83
|
2
|
0.147
|
Xan/G
|
0.98
(0.94; 1.08)
|
0.98
(0.92; 1.06)
|
1.01
(0.95; 1.03)
|
0.946
|
2
|
0.623
|
* Significance level р=0.05
Notice: Xan- xanthine, HXN – hypoxanthine, UA – uric acid, G- guanine
|
Therefore, the activity of xanthine oxidase and the level of hypoxia do not depend on the age of coal miners. The value of the ratio of Uric acid/Xanthine increased in the group of coal miners with underground experience from 3 to 5 years, followed by a decrease in the oxidative activity of xanthine oxidase, and these changes are statistically significant differences.
The intensity of purine metabolism (IPO) in blood plasma, depending on the duration of the underground experience, is presented in Table 6.
Table 6. The intensity of purine metabolism in experienced groups of coal miners (Me (Q25; Q75))
Values
|
Experienced groups
|
х2
|
df
|
P
|
0 group
|
1st group
|
2nd group
|
3d group
|
4th group
|
Xan/HXN
|
0.40
(0.37;0.42)
|
0.38 (0.37; 0.43)
|
0.39 (0.3; 0.43)
|
0.38 (0.37; 0.44)
|
0.39
(0.38; 0.42)
|
1.554
|
4
|
0.817
|
* Significance level р=0.05
Notice: Xan- xanthine, HXN – hypoxanthine
|
According to Table 6, the intensity of purine metabolism does not change in the presented groups and does not depend on the length of underground experience of coal miners (p=0.967). This is also confirmed by a comparative analysis using the Mann-Whitney U test depending on the fact of underground experience: x2=1703, Z=0.456, P=0.649. The intensity of purine metabolism also does not depend on the age of coal miners: x2=2.392, df=2, P=0.302. Thus, the intensity of purine metabolism in the blood plasma of coal miners does not depend on the age and length of underground experience.
ASF, DNA, RNA, and OMP values in blood plasma, depending on the length of the underground experience of coal miners, are presented in Table 7.
Table 7. Values of ASF, DNA, RNA, and OMP in blood plasma in experienced groups of coal miners
Values
|
Experienced groups
|
х2
|
df
|
P
|
0 group
|
1st group
|
2nd group
|
3d group
|
4th group
|
ASF
|
0.002497 (0.001857; 0.003486)
|
0.003654 (0.003092; 0.005217)
|
0.003749 (0.002972; 0.005822)
|
0.004567 (0.003132; 0.006226)
|
0.004004 (0.003176; 0.005987)
|
20.165
|
4
|
0.00*
|
DNA
|
0.000877 (0.000629; 0.001217)
|
0.001284 (0.000816; 0.001665)
|
0.000815 (0.000293; 0.001706)
|
0.001069 (0.000526; 0.002129)
|
0.001386 (0.000883; 0.00202)
|
11.904
|
4
|
0.018
|
RNA
|
0.001092 (0.000829; 0.001719)
|
0.004304 (0.002343; 0.010799)
|
0.002251 (0.000897; 0.003124)
|
0.001617 (0.001323; 0.002362)
|
0.001432 (0.001227; 0.001721)
|
46.977
|
4
|
0.00*
|
OMP
|
1.099567 (0.632035; 1.766234)
|
1.186147 (0.859307; 1.558442)
|
1.069264 (0.798701; 1.337662)
|
1.359307 (1.134199; 1.489177)
|
1.12987 (1; 1.270563)
|
6.287
|
4
|
0.179
|
* Significance level р=0.0127
|
Statistically significant changes were found for ASF and RNA in the blood plasma of coal miners, depending on the length of experience. Thus, the median of ASF values doubled in the group with more than 5 years of underground experience. RNA values increased in the group of coal miners with experience up to 3 years by 4 times, decreasing in the group of more than 5 years. The values of median DNA in plasma increased depending on the length of experience, reaching maximum values in group 4 (experience 7-10 years). However, «p» did not reach statistical significance.
The results of the logistic regression are presented in Table 8. As can be seen from the obtained data, underground experience of 7-10 years, RNA and xanthine have a statistically significant effect on the combined outcomes. That means a long underground experience increases the chance of a coal miner developing a combined outcome by 8.6 times. Uric acid, ASF and underground experience of 5-7 years are approaching a prominent level of significance, however, perhaps due to insufficient sample size and covariates, there was not enough power. Hypoxanthine, adenine, OMP, age and duration of sick leave were not included at step 1 in the logistic regression model due to the lack of influence on the combined outcomes. The predictive ability of this model was 85.4%.
Table 8. Results of logistic regression to assess the influence of independent factors on the overall outcomes of coal miners with different underground experience
Value
|
В (SE)
|
Р
|
95% CI for exp B
|
Lower
|
Exp B
|
Upper
|
Constant
|
1.721 (0.209)
|
0.000
|
|
5.593
|
|
Guanine
|
0.079 (1.254)
|
0.949
|
0.131
|
1.083
|
1.779
|
Xanthine
|
-0.051 (0.025)
|
0.044*
|
0.904
|
0.950
|
0.999
|
Uric acid
|
0.020 (0.011)
|
0.072
|
0.998
|
1.020
|
1.043
|
ASF
|
705.40 (406.301)
|
0.083
|
0.000
|
2.248
|
|
RNA
|
1.372 (0.507)
|
0.007*
|
1.460
|
3.945
|
10.660
|
Control group
|
-
|
0.113
|
|
|
|
Underground experience up to 3 years
|
0.089 (0.791)
|
0.911
|
0.232
|
1.093
|
5.149
|
Underground experience 3-5 years
|
0.712 (0.803)
|
0.376
|
0.422
|
2.037
|
9.835
|
Underground experience 5-7 years
|
1.786 (0.952)
|
0.061
|
0.922
|
5.964
|
38.561
|
Underground experience 7-10 years
|
2.159 (0.966)
|
0.025*
|
1.304
|
8.664
|
57.549
|
Variables included in the study: Guanine, Hypoxanthine, Adenine, Xanthine, UA, ASF, DNA, RNA, OMP, age, length of sick leave, length of underground experience
* Significance level р=0.05
|