Laboratory Test Reference Guide

300uL Serum

Chilled

1 - 2 g/L

A1AT is a protease inhibitor. Deficiency causes unopposed action of leukocyte elastase, causing lung disease. The threshold for lung disease seems to be 0.8 g/L

Testing is done to check for A1AT deficiency. Hereditary deficiency can cause early onset emphysema, neonatal hepatitis or juvenile cirrhosis. A1AT is an acute phase protein; deficiency may be masked if an acute inflammatory process is present. A1At may be decreased due to increased consumption: neonatal respiratory distress syndrome, severe neonatal hepatitis, pre-terminal pancreatic disease or increased loss: nephrotic syndrome or protein losing enteropathy.

Samples are referred for phenotyping (performed at LabPlus) if A1AT is < 0.8 g/L but can also be requested if unexplained liver or lung disease is present.

There is a large number of variants, Z and S are the most common variants. MM is the usual phenotype. Emphysema occurs in 70 – 90 % of patients with ZZ phenotype, as early as the 3^rd or 4^th decade, approximately 10% will have liver disease. Neonatal cholestasis is seen in 10% of ZZ patients. Patients with SZ and SS phenotypes are also at increased risk for emphysema. It is not clear whether MZ patients do have a small increase in risk for lung or liver disease or no increase in risk. MS patients are considered healthy. All patients with A1AT variants should avoid smoking.