Our study showed that routine monthly blood tests in hemodialysis patients were not always needed to modify prescriptions of medications or dialysis parameters. In the majority of our patients, the anemia and CKD-MBD blood parameters were maintained within the KDIGO targets despite the lack of a regular or monthly change in prescriptions. The median number of interventions per year targeting anemia were 5 and 4 for ESA and IV iron respectively. These changes in prescription occurred less frequently compared to the routine of monthly hemoglobin testing and triannual iron parameters’ testing. This suggests that reducing hemoglobin monitoring to every two months can be feasible in the majority of patients. Furthermore, the need for more frequent interventions in those with a lower hemoglobin level at a median of 11 g/d, higher ferritin levels at a median of 634 ng/mL and higher TSAT at a median of 28% suggests a personalized approach in this category of patients. Our study did not include C-Reactive Protein measurement to assess infection or inflammation in these patients with low hemoglobin and high ferritin; however, the high median TSAT level is not in favor of functional iron deficiency and makes inflammation less plausible. Another factor that was found associated with higher interventions for ESA in our study is dialysis vintage. This may result from the lower response to ESA when patients have been on chronic dialysis for longer period of time. This has been reported by Gaweda et al. who described an increase in ESA dose prescription with the increase of dialysis vintage from 4.6 to 7.3 years [10]. Regarding iron prescription, our regression analyses’ results showed that more interventions on IV iron were significantly associated with older age and high number of ESA changes but not associated with ferritin or TSAT levels. The fact that IV iron prescription change exceeded the number of ferritin dosage per year in our study shows that IV iron prescription was driven as well by hemoglobin levels. It is uncertain whether the iron parameters are needed three times per year or less. To the best of our knowledge, this has not been extensively studied. Very few studies tackled the number of blood tests needed per year to adapt hemodialysis patients’ prescriptions. In 2018 and 2019, two Canadian studies compared routine blood sampling performed every 6 weeks instead of every 4 weeks. They found that hemoglobin and CKD-MBD targets were reached as recommended, and the 4-week testing was not associated with lower risk of death neither cardiovascular events [2, 8]. In a small sample of 49 hemodialysis patients from the United States, Gaweda et al. found that measuring hemoglobin weekly compared to monthly reduces the error of variability and may lead to a better management of anemia [5]. However, they did not compare more prolonged intervals of sampling.
ADPKD is the most common genetic cause of ESKD, with 12.5 million cases worldwide [11, 12]. Usually, ESKD patients suffer from anemia as a consequence of decreased production of erythropoietin (EPO) by damaged kidneys. However, this does not apply to ADPKD [12]. Several studies showed a serum EPO level in ADPKD twofold higher than in ESKD of other causes along with higher hemoglobin and hematocrit values. These findings were attributable to the production of EPO by renal cysts [11, 13, 14]. Our results concur with all these studies showing higher hemoglobin values in ADPKD patients, less interventions and lower doses of ESA. Shah et al. demonstrated that higher hemoglobin reached in PKD patients was associated with a better survival with infrequent ESA administration in contrast to a higher mortality with frequent ESA administration [11]. Hence, ADPKD patients can be less frequently tested for hemoglobin than with patients with ESKD of other causes.
Interestingly, our study has shown a reduced need for measurement of PTH, serum calcium and serum phosphate. The median number of interventions ranged between 0 and 1 per year. Serum calcium in particular has not shown to affect any of the changes in prescription of alfacalcidol or phosphate binders in our sample of chronic hemodialysis patients. Curiously, smokers in our study needed more interventions with phosphate binders; this finding is aligned with Santos et al. who demonstrated higher phosphate levels in smokers [15]. In our study, higher levels of serum phosphate and PTH were significantly associated with more frequent changes in phosphate binders’ prescription but not exceeding six times per year. We also found higher PTH levels in the group of younger patients, which concurs well with the study of Yu et al. [16]. Our findings suggest that reducing calcium, phosphate monitoring to every two or three months and PTH to twice per year would be sufficient to support the physician’s decision-making regarding CKD-MBD targets in hemodialysis patients. It is noteworthy that reaching a more stable PTH level within KDOQI targets would need more frequent monthly measurements as it was shown by Greenberg et al. [6]. However, Yokohama et al. demonstrated that there is only a benefit from frequent monitoring when serum calcium, phosphate and PTH exceed their targeted values [7]. It is also important to mention that phosphate and PTH were measured in the morning in approximately half of our patients and in the afternoon in the other half. Several studies have reported a circadian variation of these two parameters [17, 18] but we did not compare the morning and afternoon groups.
In chronic hemodialysis patients, dialysis adequacy is usually assessed either by the URR or the Kt/V with a target of at least 65% and 1.2 respectively [19, 20]. A higher dose of HD is an important indicator of clinical performance and can lead to better survival as shown by Held et al. [21]. In our study, the median of URR over one year was within target, equal to 0.75 (0.72, 0.79) and no significant yearly change was noted for the session duration or the filter surface. According to the European Best Practice Guidelines (EBPG) as well as the National Kidney Foundation/Kidney Disease Outcomes Quality Initiative (NFK/DOQI), the dose of hemodialysis should be measured at least monthly [22, 23]. Nonetheless, Couchoud et al. found that 40% of dialysis units were checking urea removal less frequently than once per month [20]. We suggest to reduce the measurement of URR to 3 or 4 times per year with a personalized approach to critical patients.
Our study showed very few changes in chronic prescription of potassium dialysate or kayexalate. We found that 6% of our sample had an average serum potassium over one year above 6 meq/L. This is very close to the literature where hyperkalemia was estimated at 10% in hemodialysis patients [24]. Potassium control in CKD patients is essential since hyperkalemia is associated with the risk of cardiac arrhythmias and sudden cardiac death [25]. It is well-known as well that hyperkalemia in hemodialysis mainly results from high potassium diet [26]. Therefore, the most common intervention following hyperkalemia is promoting awareness about the patient’s potassium intake. This kind of intervention was not included in our data collection. Therefore, we suggest monitoring serum potassium every two months in hemodialysis patients except in cases of frequent hyperkalemia where monthly monitoring is preferred.
This study has several strengths. To the best of our knowledge, it is the first study in Lebanon and one of the rare studies worldwide evaluating the frequency of laboratory testing in patients on chronic hemodialysis. In addition, patients with different characteristics were evaluated. A prolonged interval of laboratory monitoring could decrease healthcare costs especially in low-income countries. The major limitation of our study is the retrospective design that confines conclusions to data collected. Data on dietary counseling would have been important when assessing interventions towards phosphate and potassium levels and this needs to be addressed in future prospective studies. The lack of data on acute supplemental sessions, transfusions and acute blood tests drawn on top of routine laboratory tests prevents us from drawing conclusions about the total number of tests per year; however, the aim of our study was to evaluate the frequency of chronic routine testing and not the tests taken in acute settings.