In this cross-sectional study, our objective was to examine the correlation between phosphorus and parathyroid hormone (PTH) levels and the occurrence of catheter-related bloodstream infections (CRBSI) in hemodialysis patients. The study encompassed individuals who had a permanent catheter inserted for dialysis initiation and were set for three weekly dialysis sessions within the designated timeframe.
Among the hemodialysis patients participating in our study, 19 out of 100 individuals had CRBSI. We found that the average levels of phosphorus and PTH were higher in individuals with CRBSI, although this difference was statistically significant only for PTH. Additionally, the average age of patients with CRBSI was higher than that of patients without CRBSI, and this difference was statistically significant. Furthermore, the calcium level among patients with CRBSI was significantly lower compared to patients without CRBSI.
Based on the logistic regression test, we determined that with each year of age, the chance of CRBSI increases by 1.1. The incidence of catheter infection in our study was 19%, which is consistent with similar studies conducted by Prachi Dubey et al., Hung et al., and Abid et al., where the rates of catheter infection were reported to be 15%, 21.4%, and 25% respectively. (8, 15, 16) .
In a 2021 study conducted in India by Prachi Dubey et al., out of 100 patients studied, 15 developed catheter-related bloodstream infections. Several risk factors for infection were identified, including older age, history of diabetes, male sex, anemia, hypoalbuminemia, hyperphosphatemia, prolongation of hemodialysis, and the location of the hemodialysis catheter(8).
In our study, we also recognized older age as an important risk factor and identified it as a prognostic factor. The existing literature has been ambiguous regarding the relationship between age and the risk of bacteremia in dialysis patients. Some studies have shown that the risk of infection is higher in the elderly(17), while others, such as the study by Murea et al., have found that the incidence of infection is higher in young dialysis patients(18).
It appears that increasing age is associated with a decrease in immunity and self-care factors, making the possibility of infection more likely. In the study by Murea and colleagues, they found that in young individuals, external mechanical factors, such as bathing, immersion in the bathtub, or engaging in sports activities, may contribute to the increased risk of infection(18). These factors could potentially compromise the integrity of the subcutaneous tunnel and facilitate the entry of bacteria from the skin, leading to the formation of bacterial colonies in the catheter. It is important to note that cultural differences may contribute to varying results in different countries.
In our study, we did not find a significant relationship between the rate of infection and the gender of the patients. This finding is consistent with the study conducted by Lee et al. (9), which also found that gender is not an effective factor in the incidence of catheter-related infection. However, it is worth noting that the study by Hoen and colleagues (10) identified female gender as a risk factor for catheter-related infection.
Regarding the calcium level, we observed that it was significantly lower in individuals with catheter infection. It is important to note that our study was cross-sectional, which means we cannot establish a cause-effect relationship in this regard. In other studies investigating the risk factors of catheter infection, the calcium level was not specifically mentioned. However, there are studies that indicate a drop in calcium levels in both normal and dialysis patients during sepsis. (19, 20).
In our study, we found that the PTH level was higher in individuals with catheter infection, and this difference was statistically significant. This risk factor for catheter infection in dialysis patients has not been extensively investigated in previous studies. However, recent research suggests that parathyroid hormone plays a role in immunological dysfunction. It has been observed that PTH receptors are present on human circulating lymphocytes (12). A study conducted by Cheng et al. in 2014 in the United States of America examined the relationship between PTH levels and inflammatory markers. They concluded that PTH levels are independently associated with several inflammatory markers (21). Another study conducted by Emam et al. in 2012 in Egypt investigated the relationship between inflammatory biomarkers and primary hyperparathyroidism. They found that the level of inflammatory biomarkers is higher in patients with asymptomatic primary hyperparathyroidism (22). These studies provide additional evidence supporting the association between PTH levels and inflammatory markers, suggesting that PTH may play a role in immunological dysfunction and potentially contribute to the risk of catheter infection in dialysis patients.
In our study, we observed that the level of phosphorus was higher in patients with infection, but this finding did not reach statistical significance. However, it is worth noting that previous research has suggested a potential link between hyperphosphatemia and immune dysfunction in hemodialysis patients. Yun et al. demonstrated a direct relationship between hyperphosphatemia and a decrease in T lymphocyte population, which may contribute to an increased risk of infection (13). Similarly, Prachi Dubey et al. identified hyperphosphatemia as a risk factor for catheter infection in their study conducted in India in 2021 (8). On the other hand, a study by Lee et al. in 2017 in Korea investigated the relationship between phosphorus levels and mortality from infection in 3226 hemodialysis patients. They found that low phosphorus levels were independently associated with an increased risk of death from infection (23). These contrasting findings highlight the need for further studies to better understand the relationship between phosphorus levels and infection risk in hemodialysis patients.
Our study had several limitations that should be acknowledged. Firstly, due to the nature of cross-sectional studies, we were unable to establish a cause-and-effect relationship between the variables examined. Secondly, the timing of the tests conducted in our study was limited to catheterization at the beginning and every three months during the study period. This limited testing schedule may not have captured the full extent of changes in phosphorus, calcium, and PTH levels.
To address these limitations, future studies should consider a cohort design with a larger sample size, allowing for more comprehensive and frequent testing. Additionally, it would be beneficial to include other inflammatory markers in the analysis to gain a more comprehensive understanding of the relationship between these markers and catheter infections.