In reply: We agree with Hung that molecular and antigen testing methods are more sensitive for Entamoeba histolytica detection than microscopy and that reliance on microscopy alone would result in under-detection. Our algorithm1 was presented the way it was for several reasons. Firstly, both molecular and antigen testing are significantly more expensive than microscopy. Secondly, as these tests can currently only detect a single pathogen, they would not replace microscopy. Most patients, especially men who have sex with men (MSM), have multiple intestinal parasites, so the more specific methods would remain an adjunct in parasite detection.2 Thirdly, the positive predictive value of any test is dependent on the prevalence of the disease. The prevalence of E. histolytica in Australia, based on current data, is less than 1% in high-risk populations, including MSM. Thus, at present, molecular and antigen tests would be more likely to give false positive than true positive results. However, we agree that our algorithm could be modified as suggested if prevalence rates were between 5% and 10%. Finally, as seen in the MSM population in Taiwan, this is not a static situation, and ongoing local surveillance is required.3
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