Prevalence of giardiasis in patients with cystic fibrosis.

A group of 107 patients with cystic fibrosis and a control group of 64 normal members of households of patients with cystic fibrosis were surveyed for Giardia lamblia cysts and trophozoites by counterimmunoelectrophoresis of fecal samples. The patient group had a significantly higher rate of infestation than the control group (28.0% vs 6.3%, P = 0.0006), and the disparity between the two groups increased with age (P = 0.005). Aside from cystic fibrosis, all risk factors examined were without influence, except for the presence of household members less than or equal to 5 years of age. We conclude that our patients with cystic fibrosis have a previously unrecognized increased prevalence of giardiasis compared with that in a control population.