Although there are many “single agent” studies that have examined correlation of infection with specific microbes, there are few studies that have compared the presence of gastrointestinal symptoms with multiple potential etiological agents. The lack of such comparative studies makes it difficult to disentangle methodology from results. In a report from Pakistan, researchers found that Blastocystis infection was more highly associated with gastrointestinal symptoms than E. histolytica or Giardia. One hundred and sixty-one patients with diarrhoea were compared to 114 age and sex matched controls. The researchers report that, “There was a marked difference in the presence of parasites between patients and controls: no parasite 42/75%, one parasite 42/15%, two or more parasites 16/10%, respectively (p < 0.001). Patients with diarrhoea were more likely to be infected with Blastocystis sp (p < 0.001), E. histolytica (p = 0.027) and E moshkovskii (p = 0.003). There was no difference in the frequency of H. pylori (p = 0.528), G duodenalis (p = 0.697) or E dispar (p = 0.425). Thirty-three patients and 27 controls had H. pylori infection. Of these, 22 patients and 6 controls were infected with Blastocystis sp (p = 0.001), 6 patients and no controls were infected with E. histolytica (p = 0.02), whilst 7 patents and 9 controls were infected with E dispar (p = 0.292)” The study was published in the British Journal of Biomedical Sciences.