STOOL - HANGING DROP METHOD

The stool hanging drop test is a microscopic method primarily used to detect motile organisms, especially trophozoites of protozoa such as Giardia lamblia. The test provides a quick and non-invasive method to observe the motility characteristics of these organisms, which helps differentiate them from non-motile forms and debris. It is typically part of stool microscopy and is useful in evaluating diarrheal illness, particularly in areas where parasitic infections are prevalent.

A small amount of fresh, liquid stool is mixed with saline on a clean glass slide, and a coverslip is placed gently over it. The slide is then examined under a microscope using high power. The drop is “hanging” between the slide and coverslip, enabling the technician to observe live organisms in motion. Rapid processing after collection is essential since trophozoites lose motility quickly outside the host.

The stool hanging drop test helps in diagnosing infections such as giardiasis and amoebiasis. In giardiasis, the characteristic “falling leaf” motility of the trophozoites can often be observed. The test also supports the identification of other motile protozoa when symptoms such as diarrhea, abdominal cramping, or flatulence are present.

This test is time-sensitive and requires immediate examination after stool collection, as delay may result in the death of trophozoites, making the test inconclusive. It also has lower sensitivity compared to antigen detection or molecular tests. Additionally, it may be difficult to differentiate between non-pathogenic and pathogenic organisms based on motility alone.

Patients are generally advised to avoid antibiotics, antidiarrheal medications, and barium studies for at least 48–72 hours before submitting a stool sample, as these can interfere with test accuracy. It is important to collect a fresh, unformed stool specimen and ensure timely delivery to the lab for optimal results.