Phosphate and parathyroid hormone (PTH) levels at the start of a hemodialysis (HD) session may vary based on the time of day they are measured, according to a recent study.
“Clinicians targeting specific phosphate and PTH goals may need to consider the time of measurement in patients who are near their clinical target and consider looking at measurements at differing times when deciding on therapy plans for patients receiving maintenance HD,” concluded a team led by Charles Ginsberg, MD, of the University of California San Diego in La Jolla.
Dr Ginsberg and colleagues analyzed data from 96,319 patients receiving maintenance HD at Fresenius Medical Care US dialysis clinics. The median serum phosphate and serum PTH levels at the start of dialysis (rounded to the nearest hour) were 5.2 mg/dL and 351 pg/mL, respectively, Dr Ginsberg’s team reported in the Journal of the American Society of Nephrology. In fully adjusted models, serum phosphate had a nadir at 11:00 AM of 4.97 mg/dL and a peak at 7:00 PM of 5.56 mg/dL. Serum PTH had a nadir at 9:00 AM or 385 pg/mL and a peak at 7:00 PM of 530 pg/mL.
“Because binary thresholds are often used to guide the intensity of treatment of phosphate and PTH concentrations, we hypothesize that many patients may be treated differently on the basis of the time they receive dialysis rather than the severity of their abnormalities in phosphate and PTH over the course of the day,” they wrote.
Although the mechanisms underlying the variation in serum phosphate and PTH over the course of the day are unclear, dietary intake of phosphate and timing of meals are likely contributors to some of the fluctuations in serum phosphate concentrations, according to the investigators.
Ginsberg C, Miller LM, Ofsthun N, Dalrymple LS, Ix JH. Differences in phosphate and parathyroid hormone concentrations over the day among patients on hemodialysis. J Am Soc Nephrol. Published online August 17, 2022. doi:10.1681/ASN.2021111493