Objective. Many infants who have experienced an apparent life-threatening event (ALTE) seem normal by the time they reach the hospital. Nevertheless, they typically undergo an extensive evaluation to rule out serious underlying conditions. The purpose of the present investigation was to determine the yield of different diagnostic tests in helping to identify the cause of the ALTE.

Methods. We reviewed test results from a consecutive series of infants who were younger than 12 months and admitted to a tertiary care academic medical center between November 1996 and June 1999 after having experienced a sudden breathing irregularity, color change, or alteration in mental status or muscle tone. For each patient, we noted whether a given test was performed, whether the result was positive, and, if so, whether the test contributed to the diagnosis, that is, suggested or helped establish the cause. We also noted whether the initial history and physical examination contributed information that eventually led to the final diagnosis.

Results. A total of 243 patients met the enrollment criteria. Of the 3776 tests ordered, 669 (17.7%) were positive and 224 (5.9%) contributed to the diagnosis. Prompted by findings from the initial clinical assessment, the following tests proved useful in patients who had a contributory history and physical examination: blood counts, chemistries, and cultures; cerebrospinal fluid analysis and cultures; metabolic screening; screening for respiratory pathogens; screening for gastroesophageal reflux; chest radiograph; brain neuroimaging; skeletal survey; electroencephalogram; echocardiogram; and pneumogram. In the remaining patients, who had a noncontributory history and physical examination, only the following tests proved useful: screening for gastroesophageal reflux, urine analysis and culture, brain neuroimaging, chest radiograph, pneumogram, and white blood cell count. Broad evaluations for systemic infections, metabolic diseases, and blood chemistry abnormalities were not productive in these patients.

Conclusions. For many tests used in the evaluation of an ALTE, the likelihood of a positive result is low and the likelihood of a contributory result is even lower. Estimates of diagnostic yield derived from the present investigation can help clinicians maximize the productivity and efficiency of their evaluation.

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