HSRT Quantitative Clinical Reasoning 2

Question 1

A drug reduces systolic BP by 8 mmHg on average (95% CI: 2–14 mmHg, p=0.01). A colleague says: 'The effect is statistically proven and clinically definitive.' Which quantitative critique is MOST appropriate?

Accepted Answer

The CI shows uncertainty from 2 to 14 mmHg; clinical significance of an 8 mmHg reduction is modest and depends on baseline BP and cardiovascular risk

Answer

Statistical significance (p=0.01) does not equal clinical significance. An 8 mmHg average with CI 2–14 mmHg may or may not be meaningful depending on clinical context.

Question 2

A clinical trial reports the Number Needed to Treat (NNT) for a new anticoagulant to prevent one stroke is 50 over 5 years. A colleague argues this means the drug is not very effective. How should you respond quantitatively?

Accepted Answer

NNT of 50 must be weighed against the NNH (Number Needed to Harm) for bleeding risk and the baseline risk of stroke — context determines clinical value

Answer

NNT must be interpreted alongside NNH, baseline risk, and the severity of the outcome — an NNT of 50 for stroke prevention may be excellent given stroke's severity.

Question 3

A clinical study reports a relative risk reduction (RRR) of 50% for a new cancer screening program. The control group event rate (cancer death) is 2%. What is the absolute risk reduction (ARR)?

Accepted Answer

1% (50% of 2%)

Answer

ARR = RRR × baseline rate = 50% × 2% = 1%. Relative risk reduction always needs to be converted to absolute terms to assess clinical impact.

Question 4

A patient asks: 'My PSA test came back positive. Does that mean I have prostate cancer?' The test has 80% sensitivity and 70% specificity. The prevalence of prostate cancer in men his age is 5%. What should the clinician communicate about the positive predictive value?

Accepted Answer

The PPV is approximately 12–15%, meaning most men with a positive PSA at this prevalence do NOT have prostate cancer

Answer

At 5% prevalence with 80% sensitivity and 70% specificity, the PPV is approximately 12–15% — the majority of positives are false positives.

Question 5

A hospital compares its 30-day mortality rate (8%) for cardiac surgery against a national benchmark (6%). Before concluding performance is substandard, which quantitative adjustment is MOST essential?

Accepted Answer

Risk-adjust for patient case mix — hospitals treating higher-acuity, comorbid patients are expected to have higher crude mortality rates

Answer

Crude mortality comparisons across institutions are only valid after risk adjustment for patient acuity, comorbidities, and case complexity.

HSRT - Health Sciences Reasoning Test Practice Test

HSRT - Health Sciences Reasoning Test Practice Test

HSRT Quantitative Clinical Reasoning 2