Which statement correctly distinguishes qualitative and quantitative testing as described?

• A. Qualitative tests yield positive/negative results; quantitative provide numeric values.
• B. Qualitative tests require calibration curves.
• C. Quantitative tests rely on reference ranges.
• D. Calibration and controls are used for quantitative tests, while qualitative tests rely on reference ranges.

Answer: (D)

Understanding the difference between quantitative and qualitative testing comes down to how results are generated and interpreted. Quantitative tests produce numeric values, so they rely on calibration curves to translate instrument signals into concentrations and on controls to ensure the assay is performing accurately from run to run. Qualitative tests yield a positive or negative result, and interpretation is based on a predefined threshold or reference value that separates normal from abnormal, rather than on a numerical concentration.

That’s why this statement is the best: it correctly pairs calibration and controls with quantitative testing, and it links qualitative results to reference ranges (cutoffs) used for interpretation. The other options misstate how calibration curves are used (they aren’t part of qualitative tests) or imply reliance on reference ranges for quantitative results in a way that isn’t the defining feature of a quantitative assay.