Enzyme-linked immunosorbent urine pregnancy tests. Clinical specificity studies

Area of Science:

• Clinical Chemistry
• Immunodiagnostics
• Reproductive Health

Background:

• Highly sensitive enzyme-linked immunosorbent assay (ELISA) kits are increasingly used for urine pregnancy testing.
• The potential for false positive results in non-pregnant individuals requires careful evaluation.
• Understanding factors contributing to false positives is crucial for accurate diagnostic testing.

Purpose of the Study:

• To evaluate the performance of six new highly sensitive ELISA urine pregnancy test kits for false positive results.
• To compare ELISA kit performance against a qualitative radioimmunoassay (RIA) procedure.
• To identify the most suitable ELISA kit for routine pregnancy testing in premenopausal patients.

Main Methods:

• Six ELISA reagent kits and one RIA procedure were used to test 100 male and 100 postmenopausal female urine specimens.
• Tests were performed to detect human chorionic gonadotropin (hCG) at specific thresholds (e.g., >50 mIU/mL).
• Medical records and routine urinalysis findings, including mucus content, were analyzed for correlations with positive results.

Main Results:

• False positive results varied significantly between ELISA kits, with Sensi-Chrome and Nimbus showing higher rates.
• Nimbus detected positives at a lower threshold (>25 mIU/mL) compared to others (>50 mIU/mL).
• A correlation was observed between mucus content in female urine and false positive hCG results, but not in male urine.

Conclusions:

• The sensitivity and specificity of highly sensitive ELISA pregnancy tests vary, leading to potential false positives.
• The Icon ELISA kit demonstrated reliable performance with no reported false positives during routine use.
• Mucus in female urine may contribute to false positive results in certain hCG detection assays.