Laboratory Procedures and Diagnostics
Core concepts
Understand sample collection, handling, and the effect of preanalytical errors (hemolysis, lipemia, delayed processing, wrong tube). Know common tests: CBC (RBC, WBC, platelets, PCV/TS), chemistry panels (BUN, creatinine, ALT, ALP, glucose, electrolytes), urinalysis (specific gravity, dipstick, sediment), and cytology. Recognize the difference between reference intervals and individual baselines. Understand anticoagulants (EDTA for hematology, heparin or citrate for coagulation, serum separator for chemistry) and the importance of labeling and chain of custody. Know quality control concepts: accuracy vs. precision, calibration, and controls.
Traps
Questions test tube selection and order of draw, and the consequences of hemolysis (falsely elevated potassium, falsely decreased some analytes). Distinguish PCV from hemoglobin, and BUN from creatinine (BUN is affected by hydration and diet; creatinine is more kidney-specific). Watch for cytology vs. histology distinctions and the difference between sensitivity and specificity.
Worked example / rule of thumb
When results are unexpected, apply the "preanalytical first" rule: check collection, tube type, hemolysis/lipemia, and processing delay before interpreting the result as disease. Rule of thumb: EDTA (purple) for CBC; serum separator (tiger-top) for chemistry.
Study focus
Prioritize tube types, hemolysis effects, urinalysis components (USG, sediment), and basic cytology interpretation. Understand accuracy vs. precision and the purpose of controls.