Detection of Helicobacter pylori antibodies in pediatric populations.

I read with interest the recent article by Sunnerstam et al. regarding their evaluation of available serologic tests for immunoglobulin G (IgG) antibodies to Helicobacter pylori in children (9). I agree that serologic methods used to determine H. pylori antibody status in children must be validated. It is well known that the performance of commercial assays designed to detect IgG antibodies to H. pylori can vary due to the bacterial antigen preparation they employ, the reference method used to confirm H. pylori status, and the population studied (3, 4). Despite the availability of enzyme immunoassays (EIAs) for serologic diagnosis of H. pylori infection, no age range is indicated for these assays, implying that these tests can be used and that their results can be interpreted equally for pediatric and adult populations. I disagree with the authors’ conclusion that “a positive serological test for H. pylori infection, particularly for children, needs to be confirmed by a reference method because of the possibility of spontaneous eradication of infection. . . .” Increased rates of acquisition of infection, as well as spontaneous clearance of infection, have been observed primarily in children under the age of 5 years (5, 6, 7, 8, 10). There was no evaluation of incidence of infection or accuracy of serology by age group presented in the paper. The urea breath test (UBT) was not performed until months after initial collection of sera for serology; therefore, transient infections were potentially missed. As a minimum safeguard, reference method testing of a group in whom spontaneous clearance is suspected to occur should have been performed at the time of serology. The population available to Sunnerstam et al. for evaluation of the four serologic tests had an extremely low seroprevalence of H. pylori infection (3%), resulting in only five samples on which to base an estimation of assay sensitivity. In addition, the confidence intervals overlap for both the sensitivities and specificities established for all four of the serologic assays evaluated, indicating that a statistically significant difference between the four EIAs was not demonstrated. Three of the four EIAs demonstrated specificities of .98% based on the data presented in the article, in contrast to the authors’ conclusion that the commercial assays gave a high rate of false-positive results. The UBT used as the reference method in the study was 100% sensitive but only 80% specific. This does not support the authors’ final recommendation that positive serology results obtained with commercial assays should be confirmed using the UBT in order to detect false positives. The potential value of serology in the diagnosis of H. pylori infection in children has been shown (1, 2). Endoscopic examination is an invasive procedure which can be difficult to perform in children. Although the UBT is noninvasive, serology is less expensive and more readily available. However, there is no guarantee that a method that has been demonstrated to be accurate for adults will perform similarly for children. I acknowledge the authors’ efforts to validate commercial serologic EIAs for H. pylori infection in children in order to establish their diagnostic utility for this group.