Investigations COVID-19

COVID-19 INVESTIGATIONS (DIAGNOSTIC & MONITORING PROTOCOL)

Appropriate investigations in COVID-19 serve four major purposes:

1. Confirm diagnosis

2. Identify differential diagnoses and co-infections

3. Assess disease severity and complications

4. Monitor progression and treatment response

Investigations should always be interpreted together with clinical status, not in isolation.

I. Imaging Investigations

Imaging is essential for detecting pulmonary involvement, staging severity, and identifying complications (e.g., ARDS, pulmonary embolism, cardiac strain).

1. Chest X-Ray (CXR) — First-Line Imaging

Indication: All symptomatic or hospitalized patients where available

Typical Findings

Advantages

• Widely available

• Bedside portable

• Useful for monitoring deterioration

2. Chest Ultrasound (Lung Ultrasound – LUS)

Particularly useful in ICU and low-resource settings.

Findings

• B-lines (interstitial syndrome)

• Pleural line irregularities

• Subpleural consolidations

• Pleural effusion (rare in COVID-19 → suggests alternate diagnosis)

3. CT Chest (High Resolution CT – HRCT)

Reserved for referral centers or diagnostic uncertainty.

Typical Patterns

• Bilateral ground-glass opacities

• Peripheral and posterior distribution

• Crazy-paving pattern

• Consolidation in severe disease

Indications

• Severe or worsening respiratory symptoms

• Suspected complications (embolism, fibrosis)

• Discordant PCR and clinical picture

Control Imaging

Repeat imaging:

• Routine follow-up: ~7 days from baseline

• Earlier if deterioration

• Later if clinically improving

II. Tests for Differential Diagnoses

Because COVID-19 mimics many tropical and respiratory diseases, co-testing is essential:

III. Routine Investigations

Baseline laboratory testing should be performed at admission.

IV. Additional Essential Investigations

Microbiological Tests

• Blood culture (suspected sepsis)

• Stool culture (diarrhea)

• Sputum culture if productive cough

Confirmatory Test

RT-PCR for SARS‑CoV‑2

Physiologic Assessment

• Arterial Blood Gas (ABG)

• ECG

• Cardiac enzymes if chest pain

Important: Do NOT delay life-saving treatment awaiting laboratory confirmation.

V. Mandatory Monitoring Tests (ON ADMISSION)

VI. Prognostic Markers

These determine likelihood of deterioration and mortality.

High-Risk Laboratory Pattern

Suggests impending critical disease:

• Rising CRP

• Rapidly rising D-dimer

• Ferritin elevation

• Lymphopenia

• Elevated LDH

• Elevated troponin

VII. Control (Follow-Up) Investigations

Monitoring frequency depends on severity.

Daily Monitoring

• Blood glucose

• Oxygen saturation

• Urine output

Every 48 Hours

• CRP

• Ferritin

• D-dimer

• Procalcitonin

Twice Weekly

• CBC

• Electrolytes

• Renal & liver function tests

Imaging Follow-Up

Clinical Interpretation Principles

1. Lab deterioration often precedes clinical deterioration

2. Rising D-dimer → suspect thrombosis

3. Rising ferritin + CRP → cytokine storm

4. Rising PCT → bacterial superinfection

5. Worsening ABG → respiratory failure

Key Takeaway

COVID-19 investigations should always be dynamic rather than static — repeated testing is more valuable than a single baseline measurement for predicting clinical trajectory.