IntraIndividual Variability in Serum Alpha-1 Antitrypsin Levels.

Area of Science:

• Pulmonary Medicine
• Clinical Chemistry
• Diagnostic Accuracy

Background:

• Alpha-1 antitrypsin (AAT) serum level measurement is a primary diagnostic step for alpha-1 antitrypsin deficiency (AATD).
• Variability in AAT serum levels between measurements and its association with inflammation markers are not well-understood.

Purpose of the Study:

• To assess the test-retest reproducibility of serum AAT levels.
• To investigate if variability in AAT measurements correlates with acute phase markers of inflammation.

Main Methods:

• Retrospective analysis of 255 patients with COPD undergoing two AAT serum level measurements.
• Measurement of white blood cell count and fibrinogen as inflammation markers during the second blood draw.
• Statistical analysis including ICC, Pearson correlation, Bland-Altman, and regression analyses.

Main Results:

• Weak between-measurement agreement for AAT serum levels (ICC=0.38, Pearson=0.34).
• Discrepancies in AAT levels led to reconsidering further investigation in 22% of patients.
• A significant correlation was found between fibrinogen levels and the second AAT measurement (r=0.21, p=0.004).

Conclusions:

• Serum AAT levels exhibit poor intra-individual reproducibility.
• This variability poses a risk for misclassifying AATD status and potentially missing diagnoses.
• Inflammation markers like fibrinogen may influence AAT serum levels.