85007

Blood Smear Examination with Manual Differential WBC Count

CPT code 85007 describes a diagnostic laboratory procedure involving the microscopic examination of a peripheral blood smear to perform a manual differential white blood cell (WBC) count. This test is typically performed when an automated hematology analyzer flags a sample for abnormalities that require human expertise or when clinical suspicion of a hematologic disorder necessitates detailed morphological assessment. The procedure begins with the collection of a whole blood sample in an EDTA-anticoagulated tube. A technician prepares a thin blood smear on a glass slide, creating a feathered edge to ensure a monolayer of cells. Once the smear is air-dried, it is stained with a polychromatic dye, most commonly the Wright-Giemsa stain, which differentiates cellular structures by color and intensity. The professional examiner then uses light microscopy, often starting at low power to assess cell distribution and then moving to oil immersion at 1000x magnification. During the manual differential, the examiner systematically identifies and classifies 100 to 200 consecutive white blood cells into their respective categories: neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Beyond simple enumeration, the examiner evaluates the morphology of each cell type, looking for toxic granulation, cytoplasmic vacuoles, Döhle bodies, or the presence of immature forms like band neutrophils, metamyelocytes, or blasts. Additionally, this procedure allows for the identification of intracellular parasites, such as malaria or babesia, and the assessment of red blood cell and platelet morphology. The results are reported as a percentage of the total white blood cell population, providing vital diagnostic information for infections, inflammatory states, and myeloid or lymphoid malignancies.

Clinical Indications

  • Evaluation of unexplained leukocytosis or leukopenia identified on automated CBC
  • Suspected acute or chronic leukemia or myelodysplastic syndromes
  • Investigation of abnormal automated hematology analyzer flags for blasts or immature cells
  • Diagnosis and speciation of parasitic blood infections such as malaria or babesiosis
  • Assessment of bacterial infections or inflammatory responses using 'left shift' indicators
  • Monitoring patients undergoing chemotherapy or bone marrow suppressive treatments
  • Evaluation of qualitative white blood cell abnormalities such as Pelger-Huët anomaly
  • Follow-up for systemic inflammatory response syndrome (SIRS) or sepsis

Procedure Steps

  1. Collection of peripheral venous blood in an EDTA (lavender-top) anticoagulant tube
  2. Preparation of a thin wedge blood smear on a clean glass microscope slide
  3. Air-drying the blood smear at room temperature to preserve cell structure
  4. Staining the slide using a polychromatic stain such as Wright-Giemsa
  5. Low-magnification (10x-40x) microscopic scan to locate the feathered edge and assess cell distribution
  6. High-magnification oil immersion (100x objective) examination for detailed cell identification
  7. Systematic counting and classification of 100 to 200 individual white blood cells
  8. Assessment and documentation of leukocyte, erythrocyte, and platelet morphology
  9. Calculation of the percentage distribution of WBC types and final reporting

Coding Guidelines

  • Do not report 85007 in conjunction with 85025 as 85025 already includes an automated differential
  • If a manual differential is performed after an automated CBC (85027) due to analyzer flags, 85007 is reported separately
  • Code 85007 is specifically for a manual count; if the differential is automated, use 85004
  • For a microscopic examination of a blood smear that does not include a manual differential count, use 85008
  • If a physician provides a formal interpretation and written report of the smear beyond the technician's count, consider code 85060
  • Modifier 91 may be applied if a repeat manual differential is medically necessary on the same day

Associated ICD-10 Codes