Screening tests for porphobilinogen are insensitive. The problem and its solution.

Area of Science:

• Clinical Chemistry
• Biochemical Diagnostics
• Urine Analysis

Background:

• Standard porphobilinogen (PBG) screening tests lack sensitivity, requiring PBG concentrations 10-20 times above normal to yield positive results.
• Early detection of conditions like acute intermittent porphyria is crucial for effective patient management.
• Existing diagnostic methods may miss cases with lower PBG levels.

Purpose of the Study:

• To develop a more sensitive screening procedure for detecting porphobilinogen (PBG) in urine.
• To improve the diagnostic accuracy for conditions associated with elevated PBG levels.
• To establish a reliable method for differentiating between normal and low-level PBG urine samples.

Main Methods:

• Development of a novel screening procedure utilizing ion-exchange resin for PBG separation from urine.
• Application of Ehrlich's reagent to the separated sample, producing a more intense color reaction.
• Spectrophotometric measurement of absorbance at 555 nm for quantitative discrimination of PBG concentrations.

Main Results:

• The new screening test demonstrated significantly higher sensitivity compared to the Watson-Schwartz test.
• The procedure successfully identified PBG in two patients with latent acute intermittent porphyria, where the Watson-Schwartz test was negative.
• Spectrophotometric analysis allowed clear differentiation between urine samples with 9 µmol/L (2 mg/L) of PBG and those with undetectable levels.

Conclusions:

• The developed screening procedure offers a highly sensitive and easy-to-perform method for PBG detection in urine.
• This enhanced sensitivity allows for earlier identification of potential porphyria cases.
• Objective spectrophotometric data provides reliable positive and negative results, improving diagnostic utility.