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Common Test-Ordering Errors
Part 1: Misordered Tests

1,25-Dihydroxyvitamin D
PTH-related Peptide
Uroporphyrinogen III Synthase

Parathyroid Hormone (PTH)

Slide 14

April 2010

Another commonly misordered endocrine test is PTH-related peptide. We believe PTH-related peptide, abbreviated PTH-RP, is often mistakenly checked when PTH is wanted. PTH, parathyroid hormone, is a routine, commonly indicated test for a variety of parathyroid gland and calcium metabolism disorders. For example, increases in PTH (as seen in primary hyperparathyroidism) result in increases in serum calcium. Conversely, in primary hypoparathyroidism, decreases in PTH result in decreases in serum calcium.

The analyte PTH-Related Peptide is indicated in only a small subset of patients, namely those with hypercalcemia associated with malignancy. In these patients, calcium levels are high, but PTH levels are suppressed. This occurs because the tumor secretes a humoral factor that mimics the action of PTH. This factor is called PTH-related peptide. To prevent unintended orders for PTH-Related Peptide, it is important for ordering individuals to carefully read the complete test name and not confuse PTH with PTH-RP. Prior to ordering PTH-Related Peptide, patients should already have undergone PTH testing. Checking for that previously performed PTH result may be another way of assuring that PTH-Related Peptide is, in fact, the test that the physician wants.

Parathyroid Hormone (PTH)


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