What test should be ordered for a child with symptoms after consuming milk?

In a child who exhibits symptoms after consuming milk, the hydrogen breath test is the most appropriate diagnostic tool for suspected lactose intolerance. This test works by measuring the amount of hydrogen in the breath after a patient consumes a lactose-rich drink. When lactose is not properly digested due to a deficiency in the enzyme lactase, it is fermented by bacteria in the colon, producing hydrogen gas as a byproduct. Elevated levels of hydrogen in the breath indicate that the lactose is malabsorbed, confirming lactase deficiency as the cause of the symptoms.

The lactose tolerance test measures the body’s response to lactose by assessing blood glucose levels after lactose ingestion. However, this test is less frequently used because the hydrogen breath test is more direct and less invasive.

A stool test for reducing substances can indicate carbohydrate malabsorption but is less specific for lactose intolerance compared to the hydrogen breath test. It is mainly used in infants and young children to assess for general carbohydrate malabsorption rather than specifically lactose.

Blood glucose tests are used to evaluate glucose metabolism and are not helpful in diagnosing lactose intolerance.

Therefore, the hydrogen breath test is the most accurate and direct method for diagnosing lactose intolerance in children experiencing symptoms after milk consumption.