What laboratory tests should be ordered in a patient experiencing sickle cell crisis?

Laboratory Tests for Sickle Cell Crisis

In patients experiencing a sickle cell crisis, a comprehensive laboratory panel should include complete blood count, markers of hemolysis, renal and liver function tests, and coagulation studies to assess the severity of the crisis and detect potential organ damage. 1

Essential Laboratory Tests

Complete Blood Count

• Hemoglobin level - to assess the severity of anemia, which results from hemolysis 1
• White blood cell count - may be elevated in acute crisis and can indicate infection or inflammation 1
• Platelet count - may be decreased in severe crisis due to consumption or sequestration 1, 2
• Reticulocyte count - to evaluate bone marrow response to hemolysis 1

Markers of Hemolysis

• Lactate dehydrogenase (LDH) - elevated levels (>1000 U/L) indicate severe hemolysis 2
• Bilirubin (total and direct) - increased due to red cell breakdown 1
• Peripheral blood smear - to identify sickled cells and schistocytes (fragmented red cells) 2
• Haptoglobin - typically decreased or absent during hemolytic episodes 3

Renal Function Tests

• Blood urea nitrogen (BUN) and creatinine - to assess for acute kidney injury, which can occur due to vaso-occlusion 1
• Electrolytes - to detect imbalances that may occur due to renal dysfunction or dehydration 1
• Urinalysis - to check for hematuria, proteinuria, or signs of urinary tract infection 1

Liver Function Tests

• Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) - may be elevated due to liver involvement 1
• Alkaline phosphatase - can be increased with hepatobiliary involvement 1

Coagulation Studies

• Prothrombin time (PT) and partial thromboplastin time (PTT) - to assess for coagulopathy 1
• D-dimer - may be elevated in severe vaso-occlusive crisis 2

Specialized Tests Based on Clinical Presentation

For Acute Chest Syndrome

• Arterial blood gas - to assess oxygenation and acid-base status 1
• Blood cultures - if infection is suspected as a trigger 1

For Priapism

• Corporal blood gas - to differentiate ischemic from non-ischemic priapism 1

For Suspected Stroke

• Review results of previous transcranial Doppler studies (especially in children) 1

For Suspected Multi-Organ Failure

• Markers of cardiac function (troponin, BNP) - if cardiac involvement is suspected 3
• Additional markers of hemolysis and organ dysfunction may be needed 3, 2

Rationale for Laboratory Testing

• Hemolysis is a central feature of sickle cell crisis, leading to anemia and potential organ damage 1
• Vaso-occlusion causes tissue ischemia, which can lead to organ dysfunction and failure 1, 2
• Infection is a common trigger for crisis and requires prompt identification 4
• Laboratory values help guide treatment decisions, including the need for transfusion, antibiotics, or more aggressive interventions like exchange transfusion 3

Important Considerations

• Baseline laboratory values should be known for comparison, as many patients with sickle cell disease have chronic abnormalities 1
• Serial monitoring of laboratory values is essential to track response to treatment 3
• Laboratory abnormalities should be interpreted in the context of the patient's clinical presentation 1
• Patients with multi-organ failure may require more frequent laboratory monitoring 3, 2

Pitfalls to Avoid

• Relying solely on hemoglobin levels to determine the need for transfusion - consider the patient's baseline hemoglobin and clinical status 1
• Overlooking signs of thrombotic microangiopathy (schistocytes, thrombocytopenia, elevated LDH) which may require plasma exchange 2
• Failing to monitor for complications of treatment, such as fluid overload or transfusion reactions 1
• Not communicating the diagnosis of sickle cell disease clearly on laboratory request forms, which may delay appropriate processing and interpretation 1