A positive shake test yields which observation?

A positive shake test yields which observation?

• A. Foam/bubbles
• B. No foam
• C. Color change
• D. Sedimentation

Answer: (A)

Foam formation on shaking indicates the presence of surfactant in the sample. When a small amount of gastric aspirate (or similar sample) is mixed with saline and vigorously shaken, surfactant lowers surface tension and allows bubbles to form and persist. The appearance of a stable layer of foam or bubbles at the surface is the positive sign, suggesting lung maturity and a lower risk of respiratory distress syndrome. If no foam forms, it suggests surfactant deficiency and a higher risk of RDS, though the result isn’t absolute.

Foam formation on shaking indicates the presence of surfactant in the sample. When a small amount of gastric aspirate (or similar sample) is mixed with saline and vigorously shaken, surfactant lowers surface tension and allows bubbles to form and persist. The appearance of a stable layer of foam or bubbles at the surface is the positive sign, suggesting lung maturity and a lower risk of respiratory distress syndrome. If no foam forms, it suggests surfactant deficiency and a higher risk of RDS, though the result isn’t absolute.