There are problems associated with using biopsy specimens . First, the biopsy size limits the volume of water droplets that can be formed on the mucus surface, thereby reducing the accuracy of the surface property determinations. Second, the biopsy surfaces are rough and heterogeneous, leading to the production of sessile drops. Finally, the trauma involved in obtaining endoscopic biopsies could disrupt the mucus surface and, hence, may not give a true indication of the in situ surface properties.
The axisymmetric drop shape analysis-diameter (ADSA-D) technique developed by Skinner et al for the determination of hydrophobicity in rabbit gastric mucosa was aimed at overcoming the problem of sessile drop formation on rough surfaces. Although the ADSA-D technique avoids the inaccuracies inherent in measuring the contact angle on rough surfaces such as gastric biopsies, it is not practical in humans, because it requires large tissue sections rather than biopsies. Animal studies on the effect of H pylori on gastric hydrophobicity have given contradictory results. Day et al have shown that H pylori had no effect on mucus surface hydrophobicity despite mucosal inflammation.