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Comparison of C-terminal and N-terminal PTH in secondary hyperparathyroidism in renal failure
Insights
N-terminal parathyroid hormone (PTH) measurements offer better clinical correlation for hyperparathyroidism in dialysis and renal failure patients. C-terminal PTH assays can yield falsely elevated results due to fragmented PTH in these populations.
Area of Science:
- Endocrinology
- Nephrology
- Clinical Chemistry
Background:
- Parathyroid hormone (PTH) plays a crucial role in calcium regulation.
- Disorders in calcium metabolism are common, particularly in patients with kidney disease.
- Accurate PTH measurement is essential for diagnosing and managing hyperparathyroidism.
Purpose of the Study:
- To compare the clinical utility of C-terminal and N-terminal PTH measurements in patients with calcium regulation disorders.
- To evaluate the accuracy of PTH assays in hemodialysis and renal failure patients.
- To determine the preferred PTH assay for diagnosing hyperparathyroidism in specific patient groups.
Main Methods:
- Measurement of both C-terminal and N-terminal PTH levels in 89 patients.
- Analysis of PTH results in patient cohorts including those with general calcium regulation disorders, hemodialysis, renal failure (creatinine clearance < 30 ml/min), and primary hyperparathyroidism.
- Correlation of PTH measurements with clinical status.
Main Results:
- In hemodialysis patients, C-terminal and N-terminal PTH trends agreed in 10, but only C-terminal was elevated in 30, and only N-terminal in 4.
- In renal failure patients, both were elevated in 5, C-terminal in 12, and N-terminal in none.
- In primary hyperparathyroidism, both were elevated in 10, C-terminal in 2, and N-terminal in 2.
Conclusions:
- N-terminal PTH determination shows better clinical correlation for hyperparathyroidism in hemodialysis and renal failure patients.
- Split products of C-terminal PTH can lead to unrealistically high PTH results in these patient populations.
- N-terminal PTH assays are recommended for improved diagnostic accuracy in renal impairment.
Abstract:
In 89 patients with disorders in calcium regulation either C-terminal or N-terminal PTH or both, were elevated. In haemodialysis patients the results of C-terminal and N-terminal PTH measurements showed the same trend in 10 patients; in 30 patients only C-terminal and in four patients only N-terminal PTH was elevated. In patients with renal failure, creatinine clearance less than 30 ml/min, both C-terminal and N-terminal PTH were elevated in five patients, C-terminal PTH in 12 patients and N-terminal PTH in none of the patients studied. Fourteen patients with primary hyperparathyroidism were studied; in ten both C-terminal and N-terminal PTH were elevated, in two only C-terminal PTH and in another two only N-terminal PTH was elevated. The results show that there seems to be a better clinical correlation for hyperparathyroidism, in haemodialysis patients and patients with renal failure, using N-terminal PTH determinations rather than C-terminal PTH determinations, because in haemodialysis patients and patients with renal failure split products of the C-terminal region of PTH give unrealistically high PTH results.