to the editor: I would like to comment on the excellent review of functional dyspepsia by Drs. Loyd and McClellan. The authors discuss the diagnosis of Helicobactor pylori infection using noninvasive tests such as serologic, stool antigen, or urea breath tests. The authors state that “serologic testing is the most common because of its wide availability and low cost, although urea breath testing is more accurate.” I would add the following information from the 2007 American College of Gastroenterology guideline on the management of H. pylori infection.¹ The serologic test has a high negative predictive value, which means that if the test is negative, the patient is very likely not infected. However, serologic testing is not recommended if the patient has ever been treated for H. pylori infection, or if the background incidence of infection is high, because serologic tests have a low positive predictive value due to the persistence (possibly for years) of antibodies to H. pylori after eradication of the infection. The American College of Gastroenterology recommends using the urea breath test or the stool antigen test for detecting active H. pylori infection because both tests have high positive and negative predictive values. The choice of test should be determined by availability and cost. The stool antigen test has been found to be the most cost-effective test ² and, unlike the urea breath test, does not expose the patient to radiation or require specialized equipment at the location of care.

I would also like to comment on the use of erythromycin as a prokinetic agent to treat gastroparesis as a cause of dyspepsia. Erythromycin is known for causing gastrointestinal pain that can be severe, which would not benefit a patient who already has dyspepsia. Instead, I would suggest a trial of azithromycin (Zithromax) because it shares the prokinetic properties of erythromycin³ but is less likely to cause painful dyspepsia as an adverse effect.

in reply: We appreciate the excellent comments offered by Dr. Keller and agree that if a patient has ever been treated for Helicobactor pylori infection, the stool antigen test or the urea breath test, if available, would be preferable to serologic testing. In one of our local hospitals, the stool antigen test is less expensive than the serum antibody test with about the same turnaround time. However, it does require stool collection and processing, which may be a barrier to test adherence for some patients.

According to a small study of patients undergoing evaluation for chronic digestive problems or gastroparesis, azithromycin stimulates antral activity similar to erythromycin, but has a longer duration of effect.¹ Though often better tolerated and requiring a less frequent dosing schedule, azithromycin costs roughly 10 times more than the same dosage of erythromycin. We encourage physicians to individualize prokinetic therapy for their patients depending on tolerance of adverse effects and cost.