Objective: The aim of the study was to investigate whether recurrent abdominal pain (RAP) in Blastocystis hominis–positive children can be treated successfully with trimethoprim-sulfamethoxazole (TMP/SMX).
Methods: From October 2004 to December 2008, all of the patients referred to the Division of Gastroenterology and Nutrition of the University Children's Hospital Zurich because of RAP and detection of B hominis in stool samples as the only pathological finding after a standard workup were offered to participate in the study. Patients were randomly assigned into 2 groups. TMP/SMX or placebo was given for 7 days in a double-blind, placebo-controlled manner. Pain index (PI) was measured with a visual analogue scale. Two weeks after completion of treatment, 3 stool samples were collected and patients were followed clinically. If B hominis was still present, metronidazole was given for 7 days.
Results: Forty patients were included; 37 finished the study (TMP/SMX n = 20, placebo n = 17). Mean PI declined from 7.1 to 3.6 for all of the patients, with a decrease from 6.9 to 4.1 in the TMP/SMX and 7.4 to 3.0 in the placebo group, irrespective of detection of B hominis after treatment. There was no statistically significant difference in PI reduction between the 2 groups. Metronidazole treatment led to a further PI decline from 3.7 to 1.9. Eradication rates were 35% (TMP/SMX) and 44% (metronidazole), compared with spontaneous clearance of 29% in the placebo group.
Conclusions: There is no advantage for TPM/SMX over placebo in the treatment of RAP in B hominis–positive children.