Laboratory Quality Control & Assurance Flashcards

Two consecutive control results both exceed the same +2SD limit. Which Westgard rule is violated, and what type of error does it suggest?

Answer: 2-2s; systematic error

The 2-2s rule flags two consecutive results beyond the same 2SD limit, which points to systematic error.

In one run, the level 1 control is +2.3SD and the level 2 control is -2.2SD. Which rule is violated?

Answer: R-4s

R-4s is violated when the range between two controls in a run exceeds 4SD, and it indicates random error.

Ten consecutive control values fall on the same side of the mean but stay within ±2SD. What does this most likely indicate?

Answer: Systematic shift, such as a calibration change

The 10x rule detects systematic error, often from a new reagent or calibrator lot or a calibration change.

On a Levey-Jennings chart, control values rise steadily over six days in a row. What is the most likely cause?

Answer: A gradually deteriorating reagent or light source

A trend is a gradual change in one direction, usually caused by slow deterioration of reagents, a lamp, or an instrument part.

A control has a mean of 100 mg/dL and an SD of 4 mg/dL. What is its coefficient of variation?

Answer: 4%

CV = (SD/mean) × 100 = (4/100) × 100 = 4%.

What is plotted on a Levey-Jennings chart?

Answer: Control values vs run or date, with mean and SD limits

Levey-Jennings charts plot control values over time against lines for the mean and ±1, 2, and 3SD.

Four consecutive control results exceed the same +1SD limit. Which rule is violated and what should the technologist suspect?

Answer: 4-1s; systematic error

The 4-1s rule detects small systematic shifts when four consecutive values exceed the same 1SD limit.