graded challenges gen.

[Alex_Krotevich]

programs must distribute specimens at least twice per year including a sufficient number of challenges (cases) to ensure adequate assessment of laboratory performance.
For programs with 10 or more challenges per event, satisfactory performance requires correct identification of at least 90% of the graded challenges in each testing event.
Laboratories with less than 90% correct responses on graded challenges...

challenges (cases) - сложные/трудные/проблемные(?)

graded challenges - "классифицированные" сложные случаи?

Спасибо.

[rendezvoir]

классифицированные случаи