The sensitivity of an individual RAPD test varied, however, with the RAPD primer used. For example, of the 30 samples interpreted as not identical based on data from tests with all four RAPD primers (one primer per test), 22 (73%) and 21 (70%) were thus identified with the primers 1254 or 1281, respectively, whereas only 14 (47%) and 11 (37%) were thus identified with the primers 1283 and 1290, respectively. Combinations of the best two and three primers gave 26/30 (87%) and 30/30 (100%) agreement, respectively, with interpretations based on all four primers. The apparent complexity of a subject's H. pylori population was not related to whether the bacteria had been cultured from biopsy versus from string test samples.