From the Guidelines
A hemoconcentrated CBC indicates a specimen collection issue rather than a disease, and to address this, a new blood sample should be collected using proper technique, ensuring adequate hydration, avoiding prolonged tourniquet application, and proper mixing with anticoagulant. This is crucial because hemoconcentration can lead to artificially elevated levels of cellular components due to decreased plasma volume, resulting in inaccurate test results 1.
Causes of Hemoconcentration
- Dehydration, which can cause fluid to be removed from the vascular space
- Excessive vacuum pressure applied during blood collection
- Prolonged tourniquet application, leading to fluid shift out of the vascular space
- Improper mixing of the blood sample with anticoagulant
Clinical Implications
Hemoconcentration can result in falsely elevated hemoglobin, hematocrit, and cell counts, potentially leading to misdiagnosis and unnecessary treatments based on inaccurate results 1. In critically ill patients, this could have significant implications, particularly in the context of anemia management and blood transfusion decisions, as evidenced by studies such as the ABC Trial and the CRIT Study 1.
Best Practice for Blood Collection
To avoid hemoconcentration, it is essential to follow proper blood collection techniques, including:
- Ensuring the patient is well-hydrated
- Limiting tourniquet application to less than one minute
- Using an appropriate needle size
- Properly mixing the blood sample with anticoagulant By adhering to these guidelines, healthcare professionals can minimize the risk of hemoconcentration and ensure accurate CBC results, which is particularly important in critically ill patients where transfusion decisions are guided by hemoglobin levels 1.
From the Research
Definition and Diagnosis of CBC Hemoconcentrated
- CBC hemoconcentrated, also known as polycythemia vera (PV), is a chronic myeloproliferative disorder characterized by increased red blood cell mass, which can lead to hyperviscosity of the blood and predispose patients to thrombosis 2.
- The diagnosis of PV is made using criteria developed by the Polycythemia Vera Study Group, which includes major criteria such as elevated red blood cell mass, normal oxygen saturation, and palpable splenomegaly 2.
- The World Health Organization's major diagnostic criteria for PV include an elevated hemoglobin or hematocrit level, abnormal results on bone marrow biopsy, and presence of the Janus kinase 2 genetic mutation, which is present in approximately 98% of cases 3.
Risk Factors and Treatment
- Patients with PV are at risk of thrombosis, and the risk is higher in those with a history of thrombosis or age greater than 60 years 4, 5.
- The main goal of therapy in PV is to prevent thrombohemorrhagic complications, and treatment includes phlebotomy to keep hematocrit below 45% and once- or twice-daily aspirin (81 mg), in the absence of contraindications 4, 5.
- Cytoreductive therapy is recommended for high-risk PV, and the first-line drug of choice is hydroxyurea, with second-line drugs including interferon-α and busulfan 4, 5.
Red Cell Mass and Hemoglobin/Hematocrit Levels
- The 2016 World Health Organization (WHO) guidelines for the diagnosis of PV emphasize the importance of red cell mass (RCM) measurements, and studies have shown that RCM is associated with increased hemoglobin (Hb) and hematocrit (Hct) levels 6.
- However, there are cases where patients with PV may have low Hb or Hct levels despite increased RCM, and vice versa, highlighting the need for careful evaluation and consideration of multiple diagnostic criteria 6.