# A Normalized Spot-Sample Estimation of α-1 Antitrypsin Clearance: The Search for a Simpler Test in Protein Losing Enteropathy

## TL;DR

Researchers tested a simple stool sample method to diagnose protein losing enteropathy but found it lacks specificity despite high sensitivity.

## Contribution

A normalized spot-sample estimation of α-1 antitrypsin clearance is proposed as a simpler diagnostic test for PLE.

## Key findings

- Spot stool α-1 antitrypsin below 0.26 mg/g had 100% sensitivity to rule out PLE.
- The specificity of the test was only 46%.
- The ratio of stool α-1 antitrypsin to serum α-1 antitrypsin and elastase did not improve diagnostic accuracy.

## Abstract

Protein losing enteropathy (PLE) is usually a diagnosis of exclusion, which requires cumbersome tests to confirm. In the quest for a simpler diagnostic test, we hypothesized that a spot stool sample estimation of α-1 antitrypsin will be sufficient to make a diagnosis of PLE, if we control for serum α-1 antitrypsin concentration and degree of stool dilution.

Consecutive patients with a clinical suspicion of PLE and who had been advised a scintigraphy study were recruited after getting informed consent. The study excluded patients less than 1 year of age, pregnant women, and those with a clinical suspicion of chronic pancreatitis. Serum α-1 antitrypsin, spot stool α-1 antitrypsin, and stool elastase was assessed in all the patients. The diagnostic value of the index test was estimated from the patients with positive scintigraphy scan compared with a negative scan, expressed as sensitivity and specificity and the area under the receiver operating characteristic curve (AUROC).

A total of 33 patients underwent scintigraphy with a clinical suspicion of PLE. Twenty patients (60%) showed tracer activity in the gut suggestive of PLE. Spot stool α-1 antitrypsin below 0.26 mg/g had a sensitivity of 100% to rule out PLE; however, the specificity was only 46%. Spot stool α-1 antitrypsin/(serum α-1 antitrypsin * elastase) ratio performed similar to spot stool α-1 antitrypsin as a diagnostic test (AUROC: 0.814 [0.61–1.0] vs. 0.796 [0.54–1.0]).

Random stool antitrypsin is a sensitive test for diagnosing PLE; however, it lacks specificity. Spot stool α-1 antitrypsin/(serum α-1 antitrypsin * stool elastase) does not provide any additional value in the diagnosis of this syndrome.