From the Guidelines
The most likely test to confirm the diagnosis in this 8-month-old girl is enzyme immunoassay of stool (option F). This child presents with classic symptoms of acute gastroenteritis - fever, vomiting, and watery diarrhea for 3 days, along with signs of dehydration including dry mucous membranes and decreased skin turgor. Given her recent entry into daycare and history of respiratory infections, a viral gastroenteritis is highly probable, with rotavirus being a common cause in this age group 1. Enzyme immunoassay of stool would detect viral antigens, particularly rotavirus, which is the leading cause of severe diarrhea in infants and young children. The clinical picture of acute onset, watery diarrhea, vomiting, and fever in an otherwise healthy child with daycare exposure strongly suggests a viral etiology rather than celiac disease (despite maternal history), bacterial infection, or parasitic infection. The incomplete immunization status also increases her risk for rotavirus infection if she hasn't received the rotavirus vaccine. Stool enzyme immunoassay provides rapid results and can guide appropriate management, which primarily involves rehydration therapy as already initiated.
Some key points to consider in the management of this patient include:
- The importance of rehydration therapy in managing acute gastroenteritis, as emphasized in the 2017 IDSA guidelines for the diagnosis and management of infectious diarrhea 1
- The role of enzyme immunoassay in detecting viral antigens, such as rotavirus, which is a common cause of severe diarrhea in infants and young children
- The consideration of epidemiologic and clinical features, such as daycare exposure and incomplete immunization status, in guiding the diagnosis and management of acute gastroenteritis
- The need for careful interpretation of laboratory results, including the use of molecular assays and culture-independent diagnostic testing, as recommended in the 2017 IDSA guidelines 1.
Overall, the enzyme immunoassay of stool is the most appropriate test to confirm the diagnosis in this 8-month-old girl, given her clinical presentation and epidemiologic risk factors.
From the Research
Diagnosis of Gastroenteritis
The patient's symptoms, such as fever, vomiting, and diarrhea, suggest a diagnosis of gastroenteritis. The patient's history of attending daycare and having multiple upper respiratory tract infections increases the likelihood of a viral cause.
Diagnostic Tests
The following diagnostic tests can be considered:
- Ultrasonography of the abdomen: This test is not typically used to diagnose gastroenteritis.
- Blood cultures: These tests are not typically used to diagnose viral gastroenteritis.
- Measurement of serum immunoglobulins: This test is not typically used to diagnose acute gastroenteritis.
- Examination of the stool for ova and parasites: This test is not typically used to diagnose viral gastroenteritis.
- Upper gastrointestinal endoscopy: This test is not typically used to diagnose acute gastroenteritis.
- Enzyme immunoassay of stool: This test can be used to diagnose viral gastroenteritis, including rotavirus and norovirus 2, 3.
Most Likely Diagnostic Test
The most likely diagnostic test to confirm the diagnosis is the enzyme immunoassay of stool, specifically for rotavirus and norovirus. Studies have shown that enzyme immunoassay is a sensitive and specific test for detecting these viruses in stool samples 2, 4, 5, 6. Additionally, immunochromatographic tests have been shown to be rapid and easy to perform, making them a useful alternative to enzyme immunoassay 4, 5, 6.
Key Findings
- Enzyme immunoassay has a high sensitivity and specificity for detecting rotavirus and norovirus in stool samples 2, 4, 5.
- Immunochromatographic tests are rapid and easy to perform, making them a useful alternative to enzyme immunoassay 4, 5, 6.
- Repeat stool testing using enzyme immunoassay does not significantly improve diagnostic yield 3.