Peripheral blood smear

Peripheral blood smear
Coinmac · CC BY-SA 3.0 · source
Name	Peripheral blood smear
Purpose	Morphologic evaluation of blood cells
Specimen	Venous blood
Technique	Microscopic examination of stained blood film
Typical turnaround	Hours to days

Peripheral blood smear

A peripheral blood smear is a laboratory test involving microscopic examination of stained venous blood to assess morphology of erythrocytes, leukocytes, and platelets. It complements automated hematology analyzers used in World Health Organization protocols and in clinical practice at institutions such as Mayo Clinic, Cleveland Clinic, and university hospitals like Johns Hopkins Hospital. Historically, the technique evolved alongside discoveries by figures connected to institutions such as Royal Society members and early pathologists affiliated with University of Paris and University of Vienna.

Introduction

Peripheral smear analysis provides direct visual assessment of blood formed elements and can detect abnormalities not apparent on automated counts. The test is routinely ordered in settings including inpatient services at Massachusetts General Hospital, outpatient hematology clinics at Memorial Sloan Kettering Cancer Center, and public health laboratories under agencies like the Centers for Disease Control and Prevention and Public Health England. It is integral to diagnostic pathways influenced by guidelines published by organizations such as the American Society of Hematology.

Indications and Clinical Uses

Indications include investigation of anemia in referrals to clinics like St. Jude Children's Research Hospital, evaluation of leukocytosis or leukopenia in patients from wards of Royal Infirmary of Edinburgh, and assessment of thrombocytopenia in transplant centers such as Fred Hutchinson Cancer Center. It aids diagnosis of hemolytic anemia, infections (e.g., malaria diagnosed in reference labs of London School of Hygiene & Tropical Medicine), hematologic malignancies managed at centers like Dana-Farber Cancer Institute, and monitoring of chemotherapy patients treated at MD Anderson Cancer Center. Smears inform decisions guided by protocols from regulatory agencies including the Food and Drug Administration when assessing blood product safety.

Procedure and Preparation

Specimen collection typically uses venipuncture performed by phlebotomy teams trained according to standards from bodies like the American Association of Blood Banks and National Health Service (England). Preparation uses anticoagulated blood (commonly with EDTA) spread on glass slides and stained using methods developed in laboratories such as the Pasteur Institute and improved by scientists at institutions like the Rockefeller University. Common stains include Wright, Giemsa, and Wright-Giemsa mixtures standardized in manuals from World Health Organization and textbooks from publishers like Oxford University Press. Quality control and slide handling follow protocols from organizations such as Joint Commission-accredited hospitals.

Microscopic Features and Interpretation

Examination evaluates red cell size, shape, color, white cell differential, and platelet estimate using bright-field microscopy models produced by companies such as Leica Microsystems and Olympus Corporation. Interpretive frameworks draw on classic descriptions from pathologists associated with Guy's Hospital and modern atlases published by researchers at University of California, San Francisco. Reporting references include morphological terms codified in consensus statements from the International Council for Standardization in Haematology and diagnostic criteria used at tertiary centers like Karolinska University Hospital.

Common Abnormal Findings

Common abnormal findings include anisocytosis and poikilocytosis described in case series from Charité – Universitätsmedizin Berlin, hypochromia seen in iron deficiency managed at clinics like Royal Melbourne Hospital, polychromasia in reticulocytosis reported by teams at Vanderbilt University Medical Center, and schistocytes in microangiopathic hemolytic anemia investigated at Hopkins-affiliated labs. Leukocyte abnormalities include left shift and toxic granulation noted in infectious disease units at Institut Pasteur, blasts characteristic of acute leukemias treated at St. Anna Children's Hospital, and smear cells associated with chronic lymphocytic leukemia described in reports from Royal Marsden Hospital. Platelet clumping and giant platelets are reported in surgical centers such as Mayo Clinic and complicating transfusion management overseen by agencies like the American Red Cross.

Limitations and Pitfalls

Limitations include preanalytical artifacts from improper anticoagulation or delayed smear preparation noted in quality reports by National Institutes of Health laboratories, observer variability discussed in studies from Harvard Medical School, and inability to quantify absolute cell counts compared with automated analyzers made by firms such as Sysmex Corporation and Beckman Coulter. Pitfalls include misinterpretation of staining artifacts resembling parasites reported in tropical medicine centers like University of Cape Town and reliance on smear alone without corroborating molecular tests available at centers like Broad Institute or cytogenetic studies performed at European Molecular Biology Laboratory.

Category:Hematology