In a school-age child with recurrent diarrhea and poor nutrient absorption, which test is the next appropriate step after a two-week lactose-free trial suggests no lactose intolerance?

In a school-age child with recurrent diarrhea and poor nutrient absorption, which test is the next appropriate step after a two-week lactose-free trial suggests no lactose intolerance?

• A. Sweat chloride test for cystic fibrosis
• B. Serologic testing for celiac disease
• C. Lactose hydrogen breath test
• D. Stool for ova and parasites

Answer: (B)

When lactose intolerance has been reasonably ruled out by a two-week lactose-free trial, persistent diarrhea with poor nutrient absorption in a school-age child points toward a possible enteropathy like celiac disease. The best next step is serologic testing for celiac disease because it is a noninvasive, sensitive, and specific screen that can identify autoimmune intestinal damage early. The typical test is IgA tissue transglutaminase antibodies, and it’s important to check total IgA as well to not miss cases with IgA deficiency; a positive result should be followed by confirmatory evaluation with a small bowel biopsy showing villous atrophy. If the serology is negative but suspicion remains, other causes can be explored, but screening for celiac disease is the most appropriate next step in this scenario. The sweat chloride test is more relevant when cystic fibrosis is suspected, which isn’t the leading consideration here; the lactose hydrogen breath test would be redundant since lactose intolerance has already been ruled out; and stool studies for ova and parasites are more pertinent if there are signs pointing to infectious or parasitic causes.

When lactose intolerance has been reasonably ruled out by a two-week lactose-free trial, persistent diarrhea with poor nutrient absorption in a school-age child points toward a possible enteropathy like celiac disease. The best next step is serologic testing for celiac disease because it is a noninvasive, sensitive, and specific screen that can identify autoimmune intestinal damage early. The typical test is IgA tissue transglutaminase antibodies, and it’s important to check total IgA as well to not miss cases with IgA deficiency; a positive result should be followed by confirmatory evaluation with a small bowel biopsy showing villous atrophy. If the serology is negative but suspicion remains, other causes can be explored, but screening for celiac disease is the most appropriate next step in this scenario. The sweat chloride test is more relevant when cystic fibrosis is suspected, which isn’t the leading consideration here; the lactose hydrogen breath test would be redundant since lactose intolerance has already been ruled out; and stool studies for ova and parasites are more pertinent if there are signs pointing to infectious or parasitic causes.