Case-based brain teasers: avoiding the misinterpretation of laboratory values

[Extract] Diagnostic reasoning is intricate and error-prone. Success hinges upon the collection and correct\ud interpretation of accurate clinical information. To make a diagnosis, the clinician should first collect a\ud good history and carry out a thorough physical examination. At this stage the patient's problems are\ud identified and appropriate differential diagnoses are listed. If necessary, further diagnostic tests (such as\ud diagnostic imaging, blood tests and urine analysis) can be done to help rule in or rule out differential\ud diagnoses. The clinician then uses inferential reasoning to refine her or his understanding of the patient's\ud problems. More specific diagnostic tests may be necessary at this stage to approach a diagnosis. A\ud 'definitive' diagnosis can be deduced once the patient’s problems are understood with a degree of\ud precision sufficient to allow accurate prognostication and formulation of an optimal therapeutic plan