From the Guidelines
Alkaline phosphatase should be checked annually in a patient with Chronic Kidney Disease (CKD) stage 4 and early mineral and bone disorder, characterized by hyperphosphatemia, with the possibility of increasing the frequency of measurements if there are elevated PTH levels or if the patient is receiving treatments for CKD-MBD.
Monitoring Intervals
- In CKD G4, serum calcium and phosphate should be monitored every 3-6 months, and PTH every 6-12 months 1.
- Alkaline phosphatase activity should be monitored every 12 months in CKD G4, or more frequently in the presence of elevated PTH 1.
Rationale
The KDIGO guideline update suggests that the frequency of monitoring serum calcium, phosphate, and PTH should be based on the presence and magnitude of abnormalities, and the rate of progression of CKD 1. While the more recent study 1 provides a broader range of monitoring intervals (every 1-12 months), the higher quality studies from the KDIGO guideline update 1 provide more specific and relevant guidance for CKD G4 patients. Therefore, annual monitoring of alkaline phosphatase is a reasonable approach for patients with CKD stage 4 and early mineral and bone disorder, with adjustments as needed based on individual patient factors.
From the Research
Monitoring Alkaline Phosphatase in CKD Stage 4
- The frequency of checking alkaline phosphatase in patients with Chronic Kidney Disease (CKD) stage 4 and early mineral and bone disorder, characterized by hyperphosphatemia, is not explicitly stated in the provided studies.
- However, according to the study 2, the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend monitoring CKD-MBD biochemical markers, including alkaline phosphatase (ALP), in patients with moderate-to-severe CKD.
- The study 2 also found that testing for ALP was somewhat higher (63.5-88.1%) compared to other biochemical markers, but the frequency of testing was still considered suboptimal in relation to KDIGO guidelines.
Bone Turnover Markers in CKD-MBD
- Bone turnover markers, such as bone-specific alkaline phosphatase, can assist in fracture risk prediction and management of osteoporosis in patients with CKD-MBD 3.
- The study 3 suggests that bone-specific alkaline phosphatase is associated with mortality and fracture rate in CKD subjects and can be used in combination with PTH to predict adynamic bone disease.
- The study 4 also highlights the importance of diagnosing and managing osteoporosis in patients with CKD, and suggests that biochemical markers, including bone-specific alkaline phosphatase, can be helpful in discriminating between osteoporosis and CKD-MBD.
Clinical Implications
- The studies suggest that monitoring alkaline phosphatase and other biochemical markers is important for managing CKD-MBD and preventing complications such as fractures and cardiovascular disease 5, 6, 2, 3, 4.
- However, the optimal frequency of checking alkaline phosphatase in patients with CKD stage 4 and early mineral and bone disorder is not clearly established, and further research is needed to determine the best monitoring strategy.