Role in the diagnosis of inflammation
A complete blood count (CBC) serves as a basic tool for the initial assessment of a patient's status. When inflammatory reactions develop in the body, the blood picture changes predictably.
The classical laboratory triad of signs of inflammation includes:
- Leukocytosis — a general increase in the number of white blood cells.
- Left shift of the leukogram — a qualitative change characterized by an increase in the proportion of band neutrophils (young forms).
- Increased ESR — acceleration of the erythrocyte sedimentation rate.
It is these three indicators that have the greatest diagnostic value in the management of patients with pneumonia (in both outpatient and inpatient settings). Moreover, in systemic processes, inflammation can affect the superficial layers of the myocardium. In such cases, a biochemical blood test additionally registers an increase in enzyme levels, particularly transaminases (ALT, AST).
Methodology and research parameters
To obtain reliable results, strict pre-analytical technique must be observed. Morning fasting blood collection is considered optimal, but for emergency indications, the test is performed at any time of the day. The patient's skin is pre-disinfected with alcohol, and exclusively disposable instruments are used for the procedure.
The source of biomaterial is:
- Capillary blood — sampling is performed with a scarifier from the pad of the left ring finger (puncture depth 2–3 mm).
- Venous blood — the cubital vein is punctured.
The parameters evaluated during the analysis are divided into three groups:
- Quantitative: total hemoglobin content, erythrocyte, platelet, and leukocyte counts.
- Qualitative: differentiated leukocyte count (white blood cell differential) and cell morphology assessment (performed by visual examination of the smear).
- Additional: ESR and reticulocyte count.
The modern standard for counting is the use of automated electronic counters. However, blood smear microscopy remains an essential method for accurately determining the leukocyte formula and detecting morphological cell abnormalities.
Interpretation principles and quality standards
The main rule for the clinician: laboratory results are evaluated only in conjunction with the actual clinical picture. Isolated numbers do not give a complete picture of the disease. Analyzing all parameters in dynamics is extremely important to monitor the response to therapy.
According to medical care quality assessment criteria, patients with suspected systemic diseases or with a verified diagnosis must undergo an expanded clinical analysis.
The mandatory scope includes:
- Expanded CBC.
- Differentiated leukocyte count (formation of the leukocyte formula).
- Reticulocyte level study.
- Microscopic examination of the blood smear.
Such patients are also indicated for biochemical screening, including the assessment of total protein, protein fraction ratios by electrophoresis, bilirubin, creatinine, urea, and enzymes (ALT, AST, LDH, alkaline phosphatase).
Class and exam questions
What does the term "left shift of the formula" mean?
This is a laboratory sign in which the percentage of band neutrophils increases in the leukocyte formula. It indicates an active inflammatory process in the body.
Can a diagnosis be made based solely on changes in the CBC?
No, interpretation principles require evaluating test results strictly in conjunction with the clinical picture of the disease and monitoring them in dynamics.
Why might transaminases increase in a biochemical analysis during inflammation?
In the pathogenesis of certain diseases, this is associated with the concomitant involvement of the superficial layers of the myocardium in the inflammatory process, leading to the release of enzymes into the blood.
What else to study on this topic
- Technique and features of capillary blood sampling
- Blood cell morphology in smear microscopy
- The significance of reticulocytes in an expanded blood count
- The role of transaminases (ALT, AST) and LDH in biochemical screening
- Protein fraction electrophoresis: indications and interpretation
Master the entire topic in the "Propaedeutics" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "White Blood Cell Differential and ESR" and 3,152 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 113 video lessons on the subject
Other topics in the "Additional Topics" section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.