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Difficulty: MediumOrdering Laboratory Tests

A 42-year-old man presents to the primary care clinic reporting a six-month history of progressive fatigue, joint pain, and decreased libido. The joint pain primarily affects the second and third metacarpophalangeal joints of both hands. His past medical history is unremarkable, and he takes no medications. Vital signs are within normal limits. Physical examination reveals generalized hyperpigmentation that is most prominent over sun-exposed areas and the palmar creases. Abdominal examination demonstrates a palpable, smooth liver edge 3 cm below the right costal margin. Laboratory testing shows a fasting blood glucose of 135 mg/dL, aspartate aminotransferase of 58 U/L, and alanine aminotransferase of 62 U/L. Which of the following is the most appropriate next step in laboratory evaluation?

  1. Transferrin saturation and serum ferritin levelsAnswer
  2. B
    HFE gene mutation analysis
  3. C
    Rheumatoid factor and anti-cyclic citrullinated peptide antibodies
  4. D
    Morning serum total testosterone and luteinizing hormone levels
  5. E
    Hepatitis B surface antigen and anti-hepatitis C virus antibodies

Answer

Transferrin saturation and serum ferritin levels
The patient's clinical presentation—progressive fatigue, specific arthropathy involving the second and third metacarpophalangeal joints, hyperpigmentation, hepatomegaly, hyperglycemia, and decreased libido (due to secondary hypogonadism from pituitary iron deposition)—is a textbook description of hereditary hemochromatosis. The most appropriate initial step in laboratory evaluation for suspected hereditary hemochromatosis is measuring iron stores using serum transferrin saturation and serum ferritin levels. If the transferrin saturation is elevated (typically >45%), the diagnosis can then be confirmed with HFE gene mutation analysis.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and identify the underlying syndrome.
The patient has a classic presentation of hereditary hemochromatosis, characterized by arthropathy (typically 2nd and 3rd metacarpophalangeal joints), bronze hyperpigmentation, hepatomegaly, new-onset diabetes mellitus, and hypogonadism (decreased libido).
Recognizing the multisystem pattern is essential to select the correct diagnostic pathway rather than pursuing isolated symptoms.
2
Determine the most appropriate initial diagnostic laboratory test for the suspected condition.
The initial screening evaluation for hereditary hemochromatosis consists of measuring serum transferrin saturation and serum ferritin levels.
Iron indices are highly sensitive screening tools. A transferrin saturation greater than 45% suggests iron overload and indicates the need for further confirmatory testing.
3
Differentiate between initial screening and definitive confirmatory testing.
HFE gene mutation analysis is identified as the definitive confirmatory step, not the initial screening test.
Standard diagnostic algorithms require demonstrating biochemical evidence of iron overload prior to ordering expensive genetic testing.

Key Concept

The initial laboratory evaluation for suspected hereditary hemochromatosis is serum transferrin saturation and ferritin levels, followed by HFE gene mutation analysis only if iron indices are elevated.
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Ordering Laboratory Tests

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