What is the role of lab tests in the workup of pediatric aphthous ulcers?

Updated: Feb 25, 2019
  • Author: Michael C Plewa, MD; Chief Editor: Russell W Steele, MD  more...
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The diagnosis of aphthous ulcers (canker sores) is usually based on the history and clinical presentation. No laboratory procedures are available for definitive diagnosis.

  • In patients with severe recurrent aphthous ulcers (RAUs), or canker sores, the clinical picture should guide laboratory testing. CBC count, a chemistry panel, and nutritional workup may be necessary.

  • Patients with suspected malabsorption or a nutritional deficiency should undergo immediate screening. Consider screening in patients presenting with a history of recurrent aphthous ulcers (canker sores) lasting 6 months or longer.

CBC counts may be within the reference range in patients with recurrent aphthous ulcers (canker sores), although some have found anemia in 21%. [3] Findings of neutropenia suggest Sweet syndrome or cyclic neutropenia; findings of leukocytosis suggest periodic fever, aphthous pharyngitis, and adenopathy (PFAPA) syndrome.

Serum iron levels may be low in 20% of those with recurrent aphthous ulcers (canker sores). [3]

If a patient is dehydrated and catabolic, urinalysis may reveal an elevated specific gravity and ketone levels. In small children, serum chemistry testing may be performed to exclude hypoglycemia and metabolic acidosis (low serum bicarbonate levels and elevated anion gap [see the Anion Gap calculator]).

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