Diagnosing poisoning by an unknown agent can be a difficult challenge. Five strategies of assessment may be used in logical sequence, however, to arrive at a diagnosis: (a) history, (b) physical examination, (c) rapid laboratory tests, (d) diagnostic trial, and (e) screening for toxins. This is illustrated by a case history, followed by discussion of a recommended approach and the utilization of these principles to arrive at a diagnosis in the case.
Initial Case History
A 41/2-year-old boy, with a history of onset of deep breathing following supper, is brought to your office by his mother. He had been alert and well all day, without fever, fully oriented, and without vomiting or diarrhea. He had been playing both in the house and garage in the morning and had spent the afternoon watching television. His temperature is 37.6°C, respiratory rate is 60 breaths per minute with deep inspiration and expiration, and pulse is 100 beats per minute and regular. He is without cyanosis. His pupils are midpoint, his lungs are clear, and his breath has no noticeable odor. What would you ask the mother in an effort to establish a diagnosis?
History
An unknown agent often can be suspected by history alone. The location of ingestion, if known, can offer clues.
Comparison of rapid laboratory tests for failure of passive transfer in the bovine