Understanding LOD, LOQ, and CV% — Accuracy Terms Explained¶
When you see "LOD 0.5 µg/dL" or "CV% < 8%" on a product sheet, what does it mean for the patient result in front of you? This page translates analytical terminology into clinical meaning.
The Four Terms¶
| Term | Definition | Clinical meaning |
|---|---|---|
| LOD (limit of detection) | Lowest concentration reliably distinguished from zero | Below this, "negative" may be uncertain |
| LOQ (limit of quantitation) | Lowest concentration measurable with acceptable precision | Below this, a number is unreliable |
| CV% (coefficient of variation) | Run-to-run consistency (precision) | Lower = more repeatable results |
| Accuracy | Agreement with a reference method | Higher = closer to the "true" value |
LOD vs LOQ — The Practical Difference¶
LOD: "the analyte is present" (detection, not reliable number)
LOQ: "the analyte is X µg/dL" (reliable quantitation)
A result between LOD and LOQ should be reported as "detected, below quantitation range" — not as a precise number.
CV% — Why It Matters for Repeatability¶
CV% measures how much repeated measurements of the same sample vary:
| CV% | Interpretation |
|---|---|
| < 8% | Excellent — minimal run-to-run variation |
| 8–10% | Good — acceptable for quantitative POCT |
| > 15% | Poor — results may fluctuate meaningfully |
For a patient monitored over days, a low CV% is essential — otherwise you cannot distinguish a real change in the patient from measurement noise.
Accuracy vs Precision¶
- Precision (CV%) = consistency (same answer each time).
- Accuracy = correctness (the right answer).
An assay can be precise but inaccurate (consistently wrong) — which is why both are validated and why correlation against a reference method (r > 0.95) is reported.
FAQ¶
Why does LOD differ between assays? LOD depends on antibody affinity for the specific analyte and fluorophore labeling efficiency — both analyte-specific.
What CV% should I expect from a good quantitative POCT? Intra-assay < 8% and inter-assay < 10% is the standard Migibio targets.
For the full validation framework, see the Research Center. For assay-specific values, see the Data Hub.
Authored by: Migibio Clinical & Scientific Affairs, Guangzhou Magic Biotech Co., Ltd.
Reviewed by: Migibio R&D Quality Committee
Last updated: 2026-08-13
Disclosure: Migibio (Guangzhou Magic Biotech Co., Ltd.) is the manufacturer of the FIA680/FIA880 analyzers and FICT reagents referenced in this content. See our Editorial & Review Policy.