The Utility of Helicobacter pylori Immunoglobulin G (IgG) and IgA Serologic Testing in Predicting Endoscopic Biopsy Results Prior to Bariatric Surgery

Brigid P O’Holleran, Anna R Ibele, MD, Rebecca M Kohler, PAC, Eric T Volckmann, MD. University of Utah

INTRODUCTION

In bariatric surgery, there is a lack of consensus regarding indications and methods for preoperative evaluation for Helicobacter pylori. We decided to review our current practice for H. pylori testing and create a protocol that would improve our efficiency and cost-savings. We propose that by increasing our threshold for obtaining endoscopic biopsies by using a serologic value higher than our institution’s laboratory cutoff for H. pylori seropositivity, we could avoid the need for unnecessary biopsy and treatment and lower the cost of preoperative patient evaluation.

METHODS AND PROCEDURES

We performed a retrospective review of the EMR of 135 patients undergoing bariatric surgery at our institution from February 2011 to September 2014. Charts were reviewed for preoperative H pylori serology and endoscopy results. Preoperative quantitative IgG and IgA levels were recorded as well as endoscopic biopsy results. Eight patients did not have records of preoperative H. pylori serology and were excluded. We used our institution’s reference range for positive serology (value greater than 1.7 ElisaValue (EV)) to determine the sensitivity and specificity of H. pylori IgG and IgA levels for detecting positive histology on endoscopic biopsy. We then compared the sensitivity and specificity of IgG and IgA levels using 4.0EV, a value higher than our institution’s laboratory cutoff for positive serology.

RESULTS

There were 71 patients who had no endoscopic biopsy, and were excluded from the sensitivity and specificity calculations in addition to the eight patients with no preoperative serology. Of the 55 patients who met inclusion criteria, 10 patients had positive biopsy for H. pylori while the remaining 45 had negative biopsy results. The sensitivity and specificity of IgA using 1.7EV as the positive cutoff were 60% and 66.67%. Using 1.7EV for IgG revealed a sensitivity and specificity of 90% and 66.67% respectively. Finally, using the proposed increased IgG level of 4.0, the specificity of the test increased to 91% while the sensitivity of the test remained stable at 90%.

CONCLUSIONS

The study results show that using a higher H. pylori serology level to trigger preoperative endoscopic biopsy will result in fewer unnecessary biopsies and thus potential cost-savings. At our institution, our current practice is to obtain both IgG and IgA serology preoperatively. For those with an elevated IgG or IgA level, it is our standard to perform an endoscopic biopsy. Based on our analysis, an IgG level of 4.0EV is more specific than the laboratory cut-off of 1.7EV, with equivalent sensitivity to the laboratory threshold for positivity. IgG levels at our proposed positivity threshold and the standard laboratory threshold were both more sensitive and specific than IgA in predicting a positive biopsy result. Additional sample size is necessary to validate our results, but we propose that to lower cost, an IgG level of 4.0 may be a better threshold to determine need for an endoscopic biopsy as part of the preoperative workup. Furthermore, unnecessary laboratory fees can be avoided by drawing only an IgG level preoperatively as IgG was a better predictor of active disease than IgA.

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