The butterfat absorption test in adults.

The usefulness of the butterfat absorption test in assessing fat absorption has been studied in 89 adult patients. In 42 patients who were shown to have steatorrhea by the criteria of the fat balance studies, 33 patients (78.6%) had abnormally low serum optical density values following butterfat ingestion. In 8 patients, steatorrhea could not be clearly explained on the basis of their underlying disease. If these 8 patients are excluded from consideration, then 28 of 34 patients (82.4%) had an abnormal response following butterfat ingestion. A maximum increase of optical density of 0.25 or less is a useful indication of fat malabsorption in adult patients.