How It Works
Study Design
CLSI EP28 specifies a pragmatic minimum design for reference interval verification:
Reference Interval VerificationVerification onlyCLSI EP28-Ed3-IG / CLSI C28-A3c≥ 20 samples
| Reference individuals | Minimum 20 healthy subjects |
| Replicates per individual | Typically 1 (replicates optional) |
| Runs | 1 run |
| Days | 1 day (minimum) |
| Pass/fail threshold | ≤ 10% of results outside the proposed reference interval |
If the reference interval is partitioned by sex, age, or another demographic variable, at least 20 reference individuals are required for each subgroup. The same 10% rule applies independently to each partition.