Placebo-Controlled Trial of Cisapride and Nizatidine in Unselected Patients With Functional Dyspepsia

A representation and interpretation of the area under a receiver operating characteristic (ROC) curve obtained by the "rating" method, or by mathematical predictions based on patient characteristics, is presented. It is shown that in such a setting the area represents the probability that a randomly chosen diseased subject is (correctly) rated or ranked with greater suspicion than a randomly chosen non-diseased subject. Moreover, this probability of a correct ranking is the same quantity that is estimated by the already well-studied nonparametric Wilcoxon statistic. These two relationships are exploited to (a) provide rapid closed-form expressions for the approximate magnitude of the sampling variability, i.e., standard error that one uses to accompany the area under a smoothed ROC curve, (b) guide in determining the size of the sample required to provide a sufficiently reliable estimate of this area, and (c) determine how large sample sizes should be to ensure that one can statistically detect differences in the accuracy of diagnostic techniques.

Symptomatology was evaluated in 304 patients referred for 24 h oesophageal pH monitoring. Of several symptoms thought to be related to gastrooesophageal reflux disease (GORD), only heartburn (68% vs 48%) and acid regurgitation (60% vs 48%) occurred in more of the patients with GORD (as determined by pH monitoring) than of those with normal pH monitoring. When heartburn or acid regurgitation clearly dominated the patient's complaints, they had very high specificity (89% and 95%, respectively) but low sensitivity (38% and 6%) for GORD. A third of the patients reported such inconclusive symptomatology at history-taking that no preliminary diagnosis about the presence or absence of GORD could be made. In the remaining 200 patients, a clinical diagnosis by history had a sensitivity of 78% and specificity of 60%. A discriminant analysis of symptoms was inferior to a history taken by an experienced gastroenterologist.

Pressure activity in the stomach and upper intestine was studied in 104 patients referred to the Mayo Clinic for evaluation of functional symptoms (nausea, vomiting, upper abdominal pain, or other dyspeptic symptoms in the absence of structural gut abnormalities). Manometric abnormalities were found in 75 patients. Forty-three of these had gastric abnormalities and 32 patients had both gastric and intestinal abnormalities. In the stomach, decreased antral phasic pressure activity after a solid meal was the most common abnormality. In the upper intestine, unpropagated bursts of phasic and tonic contractile activity were a relatively frequent abnormality but a number of other altered manometric patterns also were observed. Digestive tract symptoms were not good predictors of the presence or site of the gastrointestinal manometric abnormalities. Patients with associated neurologic, urologic, or metabolic (diabetes) disease were more likely to exhibit manometric abnormalities than were those without evidence of disease outside the gut. Almost two-thirds of the patients with symptoms and normal manometry presented features suggestive of psychiatric disease. We conclude that in patients with severe functional-type symptoms gastrointestinal manometry is a useful technique to evidence the underlying gut motor disturbance that is present in a relatively high proportion of these patients.