Guidelines for buccal smear collection in breast-fed infants

Buccal smear analysis is a noninvasive, fast, and relatively inexpensive di agnostic method. It is used commonly where rapid gender identification is n ecessary or, more recently, for detection of aneusomy, microdeletion syndro mes, and a variety of polymerase chain reaction-based molecular genetic tes ts. Previously we have shown that maternal cells can contaminate buccal sme ars taken from breast-fed infants, resulting in difficulty with test interp retation. The aim of this study was to determine optimal timing and techniq ue for buccal smear collection in breast-fed infants in order to avoid diag nostic errors. We analyzed prospectively 50 breast-fed male infants for pre sence of cells with XX signal pattern from buccal mucosa scrapings at diffe rent times after breast feeding. The efficiency of mucosal cleaning on elim ination of maternal cells was evaluated by comparing the proportion of XX c ells before and after wiping of buccal mucosa with a cotton swab. Maternal cells were present in 23 of 48 (47.9%) samples collected within 5 min of fe eding. The proportion of XX signal pattern was significantly (P = 0.001) re duced in samples collected at 30 min (8/48, P = 0.001) and greater than or equal to 60 min (2/29, P = 0.0002) after feeding. Mucosal cleaning prior to smear collection significantly decreased the number of XX positive samples from 23 of 48 to 10 of 48 (P = 0.002). Buccal smears should not be obtaine d in nursing neonates until at least 60 min after breast feeding. In additi on, prior to sample collection, buccal mucosa should be cleaned thoroughly with a cotton swab applicator. The same guidelines are applicable to older nursing infants. (C) 1999 Wiley-Liss, Inc.