Automated Analyzers: Complete Blood Count & Chemistry Panels

Can be manual or automated.
Automated analyzers measure red blood cell, platelet, and total white blood cell (leukocyte) counts.
Manual counts for exotic species and avian samples.

Impedance Analyzers: Classify cells by size using electrical current changes. Inaccurate for cats (RBCs/platelets similar size) and exotic species (RBCs/WBCs/thrombocytes similar size). Lysing agents used for WBC counts. Produce histograms.
Quantitative Buffy Coat System: Uses centrifugation and staining to estimate cellular elements (hematocrit, leukocyte, platelet concentrations). Offers partial differential count, but is a screening test only; requires blood smear for full evaluation.
Laser Flow Cytometry Analyzers: Use focused laser beams to evaluate cell size and density. Cells scatter light differently, allowing classification. Can enumerate various cell types and parameters.

Visual representation of cell number and size (size on X-axis, number on Y-axis).
Used to determine average cell size, distribution, detect subpopulations, and anomalies.
Screening tool for pathology, not diagnostic; indicates need for blood film examination. Used for quality control.

Reported as # WBC \times 10^9/L. Limited information without a differential count.
Performed manually (Leuko-tic system, hemocytometer) or by automated analyzers.
WBC Estimation: Quality control measure using differential blood smear: (\text{# WBC/high dry field } \times 2 \approx \text{# WBC } \times 10^9/L) (average 10 fields).
Automated analyzers count all nucleated cells (including nucleated RBCs), which can artificially inflate WBC count; requires mathematical adjustment.

Total & Differential Counts: Calculate absolute differential counts (Total leukocyte count \times cell %). Assess increases/decreases in specific cell types.
Morphological Abnormalities: Look for unusual cell shapes or structures.
Abnormal Cell Types (Atypical): Report if > 1-2\% present.
Immature Cell Stages: Identify any presence.

Photometry (Most Common): Spectrophotometers measure light transmitted through a solution.
- Beer's Law: Analyte concentration is directly proportional to light absorption. Higher concentration means more light absorbed, less reaches the detector.
- Absorbance Assay Methods:
  - End point: Measures concentration after a chemical reaction stabilizes, based on color change.
  - Kinetic: Measures enzyme activity at a specific time, does not reach a stable end point.
Electrochemical Methods (Ion-Selective Electrode - ISE): (e.g., potentiometers) Measure ion concentration based on voltage difference between electrodes.
Light Scatter Techniques: Detect reduction of light intensity to measure large molecules (e.g., immunoglobulins).

Results integrated into electronic patient files.
Dry Systems: Use reagent-impregnated slides/pads/cartridges (e.g., Catalyst Dx, VetTest). Mostly reflectance photometry. Less reagent handling/storage, but generally more expensive to run. Common sample rejection (lipemic, hemolyzed).
Liquid Systems: Use lyophilized or pre-prepared liquid reagents (e.g., Vetscan Rotor). Often more accurate, but require more handling/storage. Bulk reagent systems allows individual tests.
Dedicated-Use Analyzers: Utilize electrochemical methods for specific substances (e.g., blood glucose monitors).

Follow manufacturer instructions strictly.
Ensure proper warm-up periods, document maintenance to ensure reliable results and prolong machine life.