A mother presents to the family physician with her 16-year-old son. She explains, "There's something wrong with him doc. His grades are getting worse, he's cutting class, he's gaining weight, and his eyes are often bloodshot." Upon interviewing the patient apart from his mother, he seems withdrawn and angry at times when probed about his social history. The patient denies abuse and sexual history. What initial test should be sent to rule out the most likely culprit of this patient's behavior?

Sexually transmitted infection (STI) testing

A 61-year-old Caucasian woman comes to the physician for a routine health maintenance examination. She feels well. She had a normal mammography 10 months ago and a normal serum lipid profile 3 years ago. Two years ago, a pap smear and testing for human papillomavirus were performed and were negative. She had a normal colonoscopy 6 years ago. HIV testing at that time was also negative. Her blood pressure and serum blood glucose were within normal limits during a routine visit 6 months ago. She is a retired university professor and lives together with her husband. She has no children. Menopause occurred 7 years ago. Her father developed colon cancer at the age of 75 years. She does not smoke or drink alcohol. Her only medication is a daily multivitamin. She is 163 cm (5 ft 4 in) tall and weighs 58 kg (128 lb); BMI is 22 kg/m2. Which of the following health maintenance recommendations is most appropriate at this time?

Dual-energy x-ray bone absorptiometry

A 22-year-old man comes to the physician for a routine physical examination. He feels well. He has no history of major medical illness and takes no medications. His vital signs are within normal limits. Examination shows no abnormalities. Laboratory studies, including a complete blood count and a standard electrolyte panel, are within normal limits. Urine dipstick is negative for glucose; a reducing substance test result of the urine is positive. Which of the following is the most appropriate dietary recommendation for this patient?

Eliminate galactose and lactose

Increase intake of ketogenic amino acids

A 67-year-old woman presents with right leg pain and swelling of 5 days’ duration. She has a history of hypertension for 15 years and had a recent hospitalization for pneumonia. She had been recuperating at home but on beginning to mobilize and walk, the right leg became painful and swollen. Her temperature is 37.1°C (98.7°F), the blood pressure is 130/80 mm Hg, and the pulse is 75/min. On physical examination, the right calf is 4 cm greater in circumference than the left when measured 10 cm below the tibial tuberosity. Dilated superficial veins are present on the right foot and the right leg is slightly redder than the left. There is some tenderness on palpation in the popliteal fossa behind the knee. Which of the following is the best initial step in the management of this patient’s condition?

Wells’ clinical probability tool

International normalized ratio (INR)

Computerized tomography (CT) with contrast

Activated partial thromboplastin time (aPTT)

A 37-year-old woman presents to the Emergency Department after 8 hours of left sided flank pain that radiates to her groin and pelvic pain while urinating. Her medical history is relevant for multiple episodes of urinary tract infections, some requiring hospitalization, and intravenous antibiotics. In the hospital, her blood pressure is 125/83 mm Hg, pulse of 88/min, a respiratory rate of 28/min, and a body temperature of 36.5°C (97.7°F). On physical examination, she has left costovertebral tenderness and lower abdominal pain. Laboratory studies include a negative pregnancy test, mild azotemia, and a urinary dipstick that is positive for blood. Which of the following initial tests would be most useful in the diagnosis of this case?

Fractional excretion of sodium (FeNa+)

Contrast abdominal computed tomography

Blood urea nitrogen (BUN): serum creatinine (SCr) ratio

A student health coordinator plans on leading a campus-wide HIV screening program that will be free for the entire undergraduate student body. The goal is to capture as many correct HIV diagnoses as possible with the fewest false positives. The coordinator consults with the hospital to see which tests are available to use for this program. Test A has a sensitivity of 0.92 and a specificity of 0.99. Test B has a sensitivity of 0.95 and a specificity of 0.96. Test C has a sensitivity of 0.98 and a specificity of 0.93. Which of the following testing schemes should the coordinator pursue?

Test C on the entire student body followed by Test A on those who are positive

Test A on the entire student body followed by Test B on those who are positive

Test A on the entire student body followed by Test C on those who are positive

Test C on the entire student body followed by Test B on those who are positive

Test B on the entire student body followed by Test A on those who are positive

You submit a paper to a prestigious journal about the effects of coffee consumption on mesothelioma risk. The first reviewer lauds your clinical and scientific acumen, but expresses concern that your study does not have adequate statistical power. Statistical power refers to which of the following?

The probability of detecting an association when an association does exist.

The probability of detecting an association when no association exists.

The probability of not detecting an association when an association does exist.

The square root of the variance.

Avoiding unnecessary testing for USMLE Step 2 CK: High-Yield CCS Cases Lessons

Why Test Wisely? - The Core Principles

Cost of Low-Value Care: Harms of Over-testing & Solutions

Patient Safety First: Every test carries potential risks.
- False positives → patient anxiety, unnecessary invasive follow-up procedures.
- False negatives → false reassurance, delayed crucial diagnosis.
- Direct harm: radiation (CT), contrast nephropathy, procedural complications (biopsy).
Resource Stewardship: Reduces costs for the patient and healthcare system, ensuring resources are available for those who genuinely need them.
Improved Diagnostic Accuracy: Testing without clear indication (low pre-test probability) increases the chance of misleading false-positive results.

⭐ Diagnostic errors affect ~1 in 20 adults, with over half having potential for severe harm. Many stem from inappropriate test ordering or misinterpretation.

Common Pitfalls - Test Traps & Triumphs

Based on 'Choosing Wisely India' principles to curb unnecessary testing.

Commonly Ordered Test	When It's Actually Indicated (Choosing Wisely)
Routine pre-op labs (CBC, KFT, CXR, ECG)	Symptomatic patients; specific risk based on history/exam for the planned surgery.
Vit D, B12, Ferritin screening	High-risk groups or clear clinical suspicion (e.g., malabsorption, unexplained anemia). Not for general screening.
Thyroid Function Tests (TFTs)	Symptoms/signs of thyroid dysfunction (goitre, arrhythmia). Avoid in asymptomatic, non-pregnant adults.
Urine culture (asymptomatic catheterized pt)	Signs of systemic infection (fever, ↑WBC). Treating asymptomatic bacteriuria ↑ resistance.
Tumour markers (CEA, CA-125)	Monitoring diagnosed cancer. Not for screening asymptomatic individuals due to low specificity.

Clinical Decision Rules - Your Diagnostic Compass

Validated clinical decision rules (CDRs) are evidence-based tools to guide diagnostic testing, reducing patient harm and costs. They help identify low-risk patients where imaging or further tests can be safely avoided.

Wells Score: Stratifies risk for DVT & PE.
- DVT score >2 = DVT likely.
- PE score >4 = PE likely.
Ottawa Ankle & Knee Rules: For ankle/knee injuries.
- 📌 Mnemonic (Ankle): "Bony Tenderness at Malleolar or Midfoot Zones" - check posterior edge/tip of lateral/medial malleolus, navicular, or base of 5th metatarsal.
- Inability to bear weight for 4 steps is key.
NEXUS Criteria: Clears low-risk patients from C-spine imaging post-trauma.
PERC Rule: Rules out PE if all 8 criteria are negative (e.g., Age <50, HR <100, SaO2 >94%).

⭐ High-Yield: CDRs like PERC and Ottawa rules have very high sensitivity (>95%), making them excellent for ruling out disease. Their specificity is variable.

High‑Yield Points - ⚡ Biggest Takeaways

Pre-test probability is paramount; avoid tests for low-probability diseases.

Never use a "shotgun approach"; investigations must be hypothesis-driven.

Utilize clinical prediction rules (e.g., Wells score) to guide testing.

Always consider cost-effectiveness and the risk of iatrogenic harm from over-investigation.

Minimize radiation exposure (CT scans), especially in the young and pregnant.

Embrace the Choosing Wisely campaign principles to avoid unnecessary procedures.

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