A 55-year-old man from Delhi participates in a workplace screening programme for hypertension. His blood pressure is 148/92 mmHg on a single occasion. The occupational health physician schedules him for repeat BP measurement at home over 2 weeks before labeling him as hypertensive. Which screening principle best justifies this approach?

Explanation

## Screening Principle: Positive Predictive Value and Confirmation **Key Point:** A single elevated BP reading in an asymptomatic individual has low positive predictive value (PPV) due to white-coat effect, measurement variability, and high prevalence of transient elevations. Confirmation testing reduces false positives and prevents unnecessary labeling and overtreatment. **High-Yield:** Positive Predictive Value (PPV) = $\frac{TP}{TP+FP}$ In screening, PPV depends on: - Disease prevalence in the population - Test sensitivity - Test specificity A single BP reading in an asymptomatic person has: - High false-positive rate (white-coat hypertension, measurement error) - Low PPV (~30–40% for a single reading) - Confirmation by repeat measurement or home monitoring increases PPV to >80% **Mnemonic: CONFIRM** — **C**onfirm **O**ne **N**ormal **F**inding **I**s **R**arely **M**eant to **B**e **E**nough for **N**ew **D**iagnosis ### Clinical Pearl White-coat hypertension (elevated clinic BP, normal home/ambulatory BP) occurs in 20–30% of screened individuals. Confirmation prevents labeling and unnecessary lifelong treatment in these patients. ### Screening Workflow for Hypertension ```mermaid flowchart TD A[Single elevated BP reading]:::outcome --> B{Repeat BP at home<br/>or office?}:::decision B -->|Elevated on repeat| C[Confirm hypertension diagnosis]:::outcome B -->|Normal on repeat| D[White-coat hypertension]:::outcome C --> E[Initiate lifestyle/pharmacotherapy]:::action D --> F[Reassure, periodic monitoring]:::action ``` [cite:Park 26e Ch 10]