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Difficulty: MediumOrdering Laboratory Tests

An attending physician on the internal medicine teaching service is reviewing the diagnostic workup plans for four newly admitted patients with distinct systemic presentations. Match each patient's clinical vignette with the most appropriate targeted initial laboratory investigation.

  • A 32-year-old female with profound fatigue, orthostatic hypotension, unexplained hyponatremia, and hyperkalemia.Serum adrenocorticotropic hormone (ACTH) and early morning cortisol levels
  • A 71-year-old male presenting with new-onset temporal headache, jaw pain while chewing, and transient monocular vision loss.Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
  • A 48-year-old male with refractory peptic ulcer disease, multiple duodenal ulcers noted on endoscopy, and chronic diarrhea.Fasting serum gastrin level
  • A 55-year-old male exhibiting progressive cognitive decline, pupils that accommodate but do not react to light, and sensory ataxia.Cerebrospinal fluid (CSF) Venereal Disease Research Laboratory (VDRL) test

Answer

The correct pairings match the suspected diagnoses to their targeted initial tests: primary adrenal insufficiency (ACTH and cortisol), giant cell arteritis (ESR and CRP), Zollinger-Ellison syndrome (fasting gastrin), and neurosyphilis (CSF VDRL).
Each clinical vignette presents pathognomonic features of a specific disease state that requires a distinct, targeted initial laboratory test to confirm the diagnosis or guide immediate therapy.

Step-by-Step Solution

1
Analyze the first patient's symptom cluster of electrolyte derangements and hypotension.
Identified as highly suspicious for Addison's disease (primary adrenal insufficiency).
Requires baseline adrenal hormone evaluation before considering dynamic testing like a cosyntropin stimulation test.
2
Evaluate the second patient's localized cranial ischemic symptoms.
Recognized as giant cell arteritis.
Systemic inflammation must be quantified immediately to support the clinical diagnosis before or concurrent with starting high-dose steroids.
3
Assess the third patient's unusual presentation of severe peptic ulcer disease.
Suspect a gastrin-secreting neuroendocrine tumor.
Multiple duodenal ulcers and diarrhea are driven by hypergastrinemia, necessitating a fasting gastrin evaluation off proton pump inhibitors.
4
Synthesize the fourth patient's distinct neurological deficits.
Consistent with tabes dorsalis and neurosyphilis.
Requires direct analysis of the central nervous system fluid for spirochetal antibodies to confirm active central nervous system infection.

Key Concept

Targeted initial laboratory testing based on pattern recognition of specific systemic disease presentations.
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Ordering Laboratory Tests

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