Sample Type: Serum

Purpose:
A simple serological test used as a screening tool for Kala-Azar (Visceral Leishmaniasis), especially in resource-limited settings.

Principle:
Based on the reaction between serum globulins and formaldehyde (aldehyde)

In Kala-Azar patients, increased serum globulins react with formaldehyde to form a milky white gel or flocculation within minutes

Procedure Overview:
Add formalin (40% formaldehyde) to the patient’s serum

Observe for a milky white precipitate or gel formation

Interpretation:
Positive Test: Formation of white opalescence or gel within 5–10 minutes → Suggests Kala-Azar

Negative Test: No visible reaction

Limitations:
Not highly specific; false positives possible in other chronic infections

Replaced in many settings by more specific tests (e.g., rK39 rapid test)