Complex sentence: Patients with CKD and ESRD are at higher risk for infections, and PCT has been studied in these populations, who often have higher baseline levels of PCT. PCT can be dialyzed, and so levels are dependent upon when patients receive HD.
Split into simpler sentences: Patients with CKD and ESRD are at higher risk for infections, and procalcitonin has been studied in these populations, who often have higher baseline levels. Procalcitonin can be dialyzed, and so levels are dependent upon when patients receive HD.