A 28-year-old multigravida at 28 weeks of gestation is found to have blood pressure 150/95 mmHg on two occasions 4 hours apart, with no proteinuria on urine dipstick. She is asymptomatic. Which investigation is most appropriate to confirm the diagnosis of gestational hypertension and exclude preeclampsia?

Explanation

## Distinguishing Gestational Hypertension from Preeclampsia **Key Point:** Gestational hypertension is elevated BP (≥140/90 mmHg) in pregnancy **without proteinuria or end-organ dysfunction**. Preeclampsia is hypertension **plus** proteinuria (≥0.3 g/24 h or ≥30 mg/mmol creatinine) or end-organ dysfunction. ### Clinical Scenario Analysis This patient has: - Elevated BP (150/95 mmHg) on two occasions - **No proteinuria on dipstick** - **Asymptomatic** - **No clinical features of severe preeclampsia** The diagnosis is **gestational hypertension** (by definition). However, the critical next step is to **exclude subclinical proteinuria** because: 1. Dipstick proteinuria is **insensitive** for mild proteinuria (detects only ≥1+ = ≥30 mg/dL) 2. Preeclampsia may present with **minimal proteinuria** (0.3–1.0 g/24 h) that dipstick misses 3. Quantitative urine protein assessment is the **gold standard** to confirm absence of proteinuria ### Why 24-Hour Urine Protein or Protein-to-Creatinine Ratio? ```mermaid flowchart TD A["Elevated BP in pregnancy"]:::outcome --> B{"Proteinuria on dipstick?"}:::decision B -->|"Yes or ≥1+"|C["Preeclampsia suspected"]:::outcome B -->|"No"|D{"Quantitative urine protein?"}:::decision D -->|"≥0.3 g/24h or ≥30 mg/mmol"|E["Preeclampsia"]:::outcome D -->|"<0.3 g/24h"|F["Gestational hypertension"]:::outcome C --> G["Assess for end-organ dysfunction"]:::action E --> G F --> H["Monitor BP, repeat urine protein"]:::action ``` **High-Yield:** In asymptomatic hypertension without dipstick proteinuria, **quantitative urine protein** (24-hour collection or protein-to-creatinine ratio) is the investigation of choice to definitively exclude preeclampsia. ### Why Not the Other Options? | Investigation | Why Not Appropriate | |---|---| | **Serum uric acid** | Elevated uric acid (>5.5 mg/dL) suggests preeclampsia but is **not diagnostic**. It is a secondary marker of endothelial dysfunction. Not used for diagnosis in asymptomatic patients. | | **LFTs and platelets** | These assess end-organ dysfunction (HELLP syndrome). Not indicated in asymptomatic patient with no proteinuria. | | **Umbilical artery Doppler** | Fetal assessment tool; does not diagnose maternal hypertensive disorder. | **Clinical Pearl:** Protein-to-creatinine ratio (PPCR) on a random urine sample is increasingly preferred over 24-hour collection because it is convenient, faster, and equally accurate. PCCR ≥30 mg/mmol (≥0.3 g/g) is abnormal.