June 2020
Dr Marita du Plessis – Chemical Pathologist
Ampath | ampath.co.za
The Laboratory’s Role in COVID-19 Care
Laboratory testing plays a vital role in:
- Diagnosing COVID-19 using real-time reverse transcription PCR (rRT-PCR)
- Assessing disease severity
- Monitoring disease progression and guiding treatment decisions
Tests should be performed on hospital admission in patients with:
- Suspected severe COVID-19
- Significant comorbidities
Key Laboratory Tests, Expected Abnormalities, and Clinical Significance
✅ Full Blood Count (FBC)
- Abnormalities:
- Increased WBC count (rare)
- Increased neutrophils
- Decreased lymphocytes
- Normal or reduced platelets (thrombocytopenia warrants further investigation)
- Clinical significance:
- May indicate bacterial superinfection, T-cell destruction, acute inflammatory response
- Odds ratio for in-hospital death: 6.60 (WBC >10 x 10⁹/L)
✅ D-dimer
- Abnormality: Increased
- Clinical significance: Activation of coagulation and fibrinolysis
- Odds ratio: 20.04 (if D-dimer >1 mg/L)
✅ Prothrombin Time (PT)
- Abnormality: Increased
- Clinical significance: Coagulation activation
- Odds ratio: 4.62 (if PT ≥16 seconds)
✅ Arterial Blood Gas
- Abnormalities:
- Decreased pO₂ and O₂ saturation
- Hypercarbia
- Acidosis
- Clinical significance: Key in managing critically ill patients
✅ C-reactive Protein (CRP)
- Abnormality: Increased
- Clinical significance: Suggests severe viral infection, viraemia, or sepsis
✅ Procalcitonin (PCT)
- Abnormality: Increased
- Clinical significance: Indicates bacterial superinfection
- Odds ratio: 13.75 (if PCT ≥0.5 ng/mL)
✅ Ferritin
- Abnormality: Increased
- Clinical significance:
- Severe inflammation
- Thrombotic microangiopathy
- Secondary haemophagocytic lymphohistiocytosis (sHLH)
- Odds ratio: 9.10 (if ferritin >300 ng/mL)
✅ Urea & Creatinine
- Abnormality: Increased
- Clinical significance: Kidney injury
- Odds ratio for creatinine: 4.39 (if >133 µmol/L)
✅ Glucose
- Abnormality: Variable
- Clinical significance: Uncontrolled hyperglycaemia worsens prognosis in both diabetic and non-diabetic patients
✅ Albumin
- Abnormality: Decreased
- Clinical significance: Suggests impaired liver function
✅ Total Bilirubin, ALT, AST
- Abnormalities: Increased
- Clinical significance: Liver injury and/or general organ damage
✅ Lactate Dehydrogenase (LDH)
- Abnormality: Increased
- Clinical significance:
- Liver or pulmonary injury
- Widespread tissue damage
✅ Creatine Kinase (CK)
- Abnormality: Increased
- Clinical significance: Muscle injury
✅ High-Sensitivity Troponins (hsTroponin or hsTn)
- Abnormality: Increased
- Clinical significance: Cardiac injury
- Odds ratio: 80.07 (if hsTn >99th percentile)
Additional Inflammatory Marker: Interleukin-6 (IL-6)
- IL-6 is recommended as a marker for cytokine storm syndrome, often seen in patients with severe COVID-19.
Markers Predictive of Disease Severity and Mortality
The following lab findings are associated with worse outcomes:
- High neutrophil-to-lymphocyte ratio (>1.4)
- Persistent low counts of:
- CD4
- CD8
- CD19+ B cells
- NK cells (CD16+CD56+)
- Increased levels of:
- D-dimer
- Creatinine
- LDH (>245 U/L)
- CK
- Ferritin
- CRP
- IL-6
- Procalcitonin
- hsTroponin
- Glucose (hyperglycaemia)
Top Predictors of In-Hospital Death
According to Zhou et al. (2020), the strongest independent risk factors for death were:
- Increased age
- D-dimer >1 mg/L
- High SOFA score (Sequential Organ Failure Assessment)
These markers help identify high-risk patients early.
References
- International Federation of Clinical Chemistry (IFCC), 2020
- BMJ Best Practice, 2019
- Zhou F. et al., Lancet, 395: 1054–62
- Favaloro & Lippi, 2020 – Thieme Medical Publishers
- Liu Y. et al., Science China Life Science, 2020
- He R. et al., Journal of Clinical Virology, 2020
- Velavan TP & Meyer CG, Int. J. Infect. Dis., 2020
- Xu B. et al., Chin Journal of Infection, 2020
📌 Please contact your local Ampath pathologist for more information or patient-specific guidance.
Continue Reading