The mean age of our patients indicated that our studied population was young. Moreover, in similar cross-sectional studies by Adly et al., Economou et al., and Tanus et al. the age of patients with beta-thalassemia major was younger (15–17). This may be due to the fact that we included the mean age of patients with sickle cell thalassemia, major thalassemia, and intermedia thalassemia, which affected our final results, whereas Adly et al. included major and intermedia thalassemia and Ecnomou et al. included only major thalassemia patients, as did Tanus et al. On the other hand, in the study presented by Voskaridou et al., the mean age of sickle and thalassemia patients was higher (42.1 years)(18). These findings were inconsistent with our study, which may be due to the fact that thalassemia patients have a lower life expectancy than sickle-cell patients(19).
Moreover, we found that out of 66 patients, 18 cases (27.3%) had microalbuminuria. Similar results were reported in previous studies(18, 20). Voskaridou et al. stated that proteinuria was determined in almost 30% of patients and increased with age(18). Quinn et al. also reported a higher incidence of patients with albuminuria (59%) and likewise confirmed the association between albuminuria and age(20). Furthermore, Economu et al. stated that 24% of patients demonstrated impaired renal function with proteinuria(16). Our study also revealed a strong correlation between the serum ferritin level and microalbuminuria (p value = 0.005), indicating that the serum ferritin level in patients with microalbuminuria is significantly higher than that in patients without microalbuminuria, which was not mentioned in previous studies.
In our study, β2M levels were above the normal range (> 0.3 according to our laboratory reference range) in 10 patients (15.15%). Previous studies reported a higher incidence of increased β2M levels (16, 21, 22). Economou et al. reported an increased excretion of β2M in 33.5% of patients with major thalassemia (16). On the other hand, Deveci et al. measured the ratio of β2M to Cr (BCR) to assess renal tubular damage, which was increased in 64.6% of patients with beta-thalassemia (21). Moreover, in the study by Safaei et al., abnormal levels of urinary β2M were also found in 44 patients (55%) (22). These differences in β2M levels reported in previous studies may be due to the improvement in the medical care of thalassemia patients, which probably caused a reduction in the extent of proximal tubular damage. Our study also showed that there was no significant correlation between serum ferritin level and β2M. This finding was in agreement with the study of Safaei et al. (23). In contrast, Adly et al. reported that there was a positive correlation between serum ferritin and urinary β2M in all thalassemia patients(15).
Moreover, The mean serum Cr level in our study population was not within the normal range, which was in contrast to Adly et al. (15). This finding was in agreement with Voskaridou et al. and Mahmoud et al.’s studies(18, 23).
In our study, abnormal values of FENa, FECa, and FEUa were observed. Similarly, Mohkem et al. reported abnormal values of FENa, FEK, and FEUa (24). On the other hand, some studies reported that the values of FENa and FEK did not differ between patients with beta-thalassemia and the control group(15, 25, 26).
Our results showed that there was a significant and negative correlation between serum ferritin level and FENa, FECa, FEP, FEMg, and FEUa. To the best of our knowledge, there has been no study mentioning the correlation between fractional excretion of electrolytes and serum ferritin level in patients with thalassemia. On the other hand, some studies found a significant correlation between serum ferritin level and other predictors of renal damage and prevented us from making further comparisons and analyses(17, 21, 23). Tanus et al. and Mahmoud et al. reported a significant correlation between serum ferritin levels and urinary N-acetyl-b-D-glucosaminidase (UNAG)(17, 23). Moreover, Deveci et al. showed that there was no correlation between serum ferritin levels and renal damage (predictor factors included the ratio of urine albumin and β2M to Cr) in beta thalassemia patients(21).
The current study had some limitations that should be acknowledged. First, it was a cross-sectional study with a small sample size. We suggest conducting similar studies with a larger study population for a longer period of time in the future. Another limitation was that during this study, due to international sanctions, it was not possible to use NAG measurement kits, and they were practically rare.
In conclusion, we realized that serum ferritin levels had a strong correlation with FeNa, FeUa, FeCa, FeP, and FeMg with a negative correlation coefficient in patients with hemoglobinopathies, indicating that as ferritin levels increased, these variables decreased and vice versa. We also found a significant relationship between the serum ferritin level and microalbuminuria, indicating that the serum ferritin level in patients with microalbuminuria is significantly higher than that in patients without microalbuminuria. Further studies are needed to investigate the relationship between renal function markers and serum ferritin levels in thalassemia patients.