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

p=0.01 confirms the finding is highly reliable, making the colleague correct

Answer

The CI should be narrowed to 6–10 mmHg before clinical recommendations are made

Answer

Statistical significance always implies clinical significance in hypertension research

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 of 50 is very high and definitively indicates the drug is ineffective

Answer

NNT is only meaningful when compared to placebo studies, not active comparators

Answer

NNT of 50 should be converted to absolute risk reduction before any conclusion is drawn

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

50% (same as the RRR)

Answer

48% (100% minus 2% minus 50%)

Answer

Cannot be calculated from this information alone

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

Because sensitivity is 80%, the patient almost certainly has cancer

Answer

The PPV is 70%, the same as the specificity

Answer

PPV cannot be estimated without the specific cutoff value used

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

Report the finding immediately to hospital administration as a quality failure

Answer

Exclude outlier cases to normalize the rate to the benchmark

Answer

Increase sample size by including non-cardiac surgical cases

Question 6

A dietitian calculates that a patient needs 1800 kcal/day. The patient reports eating an average of 1200 kcal/day. Which quantitative statement BEST characterizes the deficit?

Accepted Answer

The patient has a 600 kcal/day deficit (33% below requirements), which if sustained over one week creates a cumulative deficit of 4200 kcal

Answer

The patient is eating 1200 kcal/day, which is within the healthy range for adults

Answer

The 600 kcal deficit will cause immediate clinical deterioration

Answer

The deficit equals approximately 30 grams of fat per day