Which of the following are considered pre-analytical variables in laboratory testing?

• A. Patient factors (e.g., fasting state, posture)
• B. Sample quality (hemolysis, lipemia, icterus)
• C. Collection timing
• D. All of the above

Answer: (D)

Pre-analytical variables are factors that occur before the actual analysis and can change test results. These include what the patient does, how the sample is obtained and handled, and when the sample is collected. Patient factors like fasting state and posture can affect test outcomes—for example, fasting influences glucose and lipid measurements, and upright posture can cause hemoconcentration. Sample quality issues that arise during collection or handling, such as hemolysis, lipemia, or icterus, can interfere with many assays by changing color, turbidity, or releasing intracellular components. The timing of collection matters because some analytes vary with time of day or in relation to meals. Since all of these occur before analysis, they are all considered pre-analytical variables.