Diagnostic Reasoning Flashcards

A child presents with a barking cough, stridor, and low-grade fever after a URI. The MOST likely diagnosis is:

Answer: Croup (laryngotracheobronchitis)

The classic triad of barking cough, inspiratory stridor, and low-grade fever following URI is diagnostic of croup, caused most often by parainfluenza virus.

A 65-year-old with a 30 pack-year smoking history presents with a FEV1/FVC ratio of 0.65 post-bronchodilator. The MOST likely diagnosis is:

Answer: Chronic obstructive pulmonary disease (COPD)

A post-bronchodilator FEV1/FVC ratio <0.70 in a smoker confirms the obstructive pattern required for GOLD criteria COPD diagnosis.

The FNP notes café-au-lait spots (>6, >15mm) in an adult patient. This finding raises suspicion for:

Answer: Neurofibromatosis type 1

Six or more café-au-lait macules larger than 15 mm in adults are a major diagnostic criterion for neurofibromatosis type 1 (NF1).

A patient has a positive ANA titer of 1:320 with a butterfly rash across the cheeks and nose. The FNP suspects:

Answer: Systemic lupus erythematosus (SLE)

A malar (butterfly) rash sparing the nasolabial folds combined with a high-titer ANA are classic features of SLE.

A 45-year-old woman presents with fatigue, weight gain, constipation, cold intolerance, and bradycardia. The BEST initial diagnostic test is:

Answer: TSH level

TSH is the most sensitive test for thyroid dysfunction; an elevated TSH confirms primary hypothyroidism before further testing.

A patient presents with painful vesicles in a dermatomal distribution on one side of the trunk. The FNP diagnoses herpes zoster and notes the MOST important reason to treat promptly with antivirals:

Answer: To reduce the severity and duration of postherpetic neuralgia

Early antiviral treatment (within 72 hours) reduces the risk and severity of postherpetic neuralgia, the most common complication of herpes zoster.