Significance of acellular smears in conjunctival impression cytology

Conjunctival xerosis is a marker for vitamin A deficiency. Conjunctival impression cytology (CIC) is a widely used technique to detect xerosis in field studies. Inadequate and acellular samples are generally considered technical failures and are treated as uninterpretable. The purpose of this study is to determine the significance of acellular smears in the detection of vitamin A deficiency.

CIC with transfer (CICT) and blood samples were collected from freshly diagnosed cancer patients and healthy controls. CICT smears were classified as cellular or acellular. Serum vitamin A levels were tested by high-performance liquid chromatography. CICT results were compared with vitamin A levels.

CICT was collected from 1,694 subjects. There were 118 (7%) acellular smears, i.e. 99 in patients and 19 in controls. Serum vitamin A levels were available in 112 of these subjects. Levels <20 µg/dl were seen in 82.1% of the subjects with acellular smears and in 18.9% of the subjects with cellular smears (p < 0.001). Of the gastrointestinal and hepatobiliary and hematologic cancers, 15.6% and 10.5% showed acellular smears, respectively.

Acellular smears in conjunctival imprint cytology may indicate hypovitaminosis A, provided technical failure to obtain cellularity is ruled out.