Metabolic
Although in-born errors of metabolism are uncommon diagnoses, they must be considered as a cause of ALTE in the appropriate clinical context as they are reported in 1.5% to 7.7% of ALTE patients.7 Clinical clues suggesting an inborn error of metabolism include poor weight gain, unusual body odors (eg, of urine or sweat), symptom onset with institution of formula or diet change (eg, protein introduction), metabolic acidosis, hypoglycemia, thrombocytopenia, and neutropenia. Any of these clinical clues can point the practitioner toward a metabolic workup.
Nontraumatic Injury
The EP must always be watchful for signs of nonaccidental trauma in pediatric patients, as abusive head injury is diagnosed in 1% to 3% of ALTE case presentations.6,16 A retrospective review found vomiting, irritability, and a documented 911 call to be risk factors associated with increased likelihood of abusive head trauma.16 Again, a thorough history and physical examination is prudent in all ALTE patients, and close attention should be paid to inconsistent or poorly explained histories and findings such as bruising or burns. Fictitious illness has also been documented in cases of ALTE in less than 3% of all cases, and should be considered especially in cases of repeated ALTEs witnessed by the same caregiver.7
Hematologic and Idiopathic
Almost a quarter of patients presenting with ALTE are found to have low hemoglobin for their respective age, with higher rates of anemia in patients with repeat ALTEs.6 However, there is no clear causative effect between anemia and ALTE. Moreover, in 25% to 50% of ALTE cases, there is no clear diagnosis and therefore the cause is considered idiopathic in nature.7,8
Workup
While there is no standardized workup for ALTE, a careful history and physical examination should help guide diagnostic testing ordered in the ED. A retrospective study of 243 patients found that in 49%, the history and physical examination suggested an etiology that was confirmed by diagnostic testing (eg, a patient presenting with wheezing and rhinorrhea, who has a positive RSV antigen).17 Another 21% of patients were diagnosed solely on history and physical examination findings. While these patients may have had diagnostic tests performed, the tests did not contribute to the final diagnosis. In this study cohort, a final diagnosis was made by positive diagnostic tests alone in only 14% of patients with both nonspecific histories and physical examination findings. As previously mentioned, these findings underscore the critical role that history and physical examination play in the diagnosis of ALTE.
As no obvious pathology is found in up to half of all ALTE cases, the EP must decide which tests will most likely be of diagnostic utility. Diagnostic tests are ordered in a majority of patients18 and a chest X-ray is one of the most frequently positive tests.4,19
A positive test, however, does not necessarily lead to a diagnosis for the etiology of the ALTE. Only approximately one-third of the positive tests in the previously cited study were determined to contribute to the final diagnosis.17 The list of possible diagnostic tests for ALTE patients is lengthy and, at times, invasive. For this reason, EPs should perform focused testing based on the concerning elements in the history and physical examination rather than order a set of specific screening labs for each infant.
Need for Admission
Disposition is often a difficult decision in treating ALTE patients (and their families). Infants often look well and are acting normally by the time they arrive in the ED and remain well-appearing throughout the ED stay. If a thorough history, physical examination, and focused diagnostic testing uncover no specific etiology, the EP must decide whether to admit the patient for observation or discharge him or her home with instructions for pediatric follow up.
The majority of patients presenting to the ED with ALTE are admitted to inpatient services, many for overnight observation.13,20,21 Since 12% to 23% of patients with ALTE experience a repeat event or clinical condition requiring intervention,13,20,21 multiple studies have attempted to design a clinical decision rule to determine high-risk infants requiring admission.13,20,21 One small study had 100% sensitivity for infants requiring admission with two criteria: a history of multiple ALTEs and/or age younger than 1 month.21 Another study suggested high-risk criteria include prematurity and abnormal physical examination in the ED.13 To date, there are no well-validated clinical decision rules allowing for risk stratification of ALTE infants to home. As such, most infants with ALTE will be admitted for observation, but the appropriate disposition is best made in a collaborative decision-making process involving both the caregivers and the child’s pediatrician.