Final answer:
The measurement of GGTP is crucial when ALP is moderately elevated because it can identify cholestasis or liver dysfunction, which may not be delineated by ALP alone. GGT is liver-specific and can differentiate the cause of liver enzyme elevation, particularly when associated with alcohol toxicity or liver damage.
Step-by-step explanation:
A moderately elevated alkaline phosphatase (ALP) of unclear etiology should be followed up with y-glutamyl transpeptidase (GGTP). This is because GGTP is considered a more sensitive marker for cholestatic damage than ALP and is reasonably specific to the liver. It may detect even minor, sub-clinical levels of liver dysfunction and help identify the cause of an isolated elevation in ALP. Elevated levels of GGT can indicate alcohol toxicity and acute liver damage. While ALP is also present in bone and placental tissue, a concurrent increase in GGT often confirms the hepatobiliary origin of the elevated ALP.
Blood testing can examine liver function and elevated levels of certain enzymes, such as ALP, alanine aminotransferase (ALT), and aspartate aminotransferase (AST), can suggest a possible liver problem. If there is an isolated elevation in ALP, GGT can provide additional evidence to help pinpoint whether the elevation is due to liver disease. This allows for more accurate diagnosis and treatment planning.
For example, in cases of alcoholism, liver damage might be indicated by raised levels of GGT. Similarly, a GGT elevation alongside ALP might suggest an infiltrative liver disease, obstructive liver pathology, or cholestasis. Thus, measuring GGT is essential in assessing liver health and narrowing down the causes of liver enzyme alterations.