Understanding the terms used to report HCV RNA levels helps ensure accurate interpretation of test results

Roche HCV RNA tests report specimen results in 1 of 4 ways:

HCV RNA result interpretation

A value of “<LOD” or “LOD” is not a reported value by real-time PCR assays. Limit of Detection (LOD) is defined as the lowest concentration of HCV RNA that can be confidently detected 95% of the time. Below the LOD, HCV RNA is detected with decreasing probability (95% to 0%) as the viral titer drops from the LLOQ to negative (15 IU/mL to 0 IU/mL). Therefore, a result of “<LLOQ IU/mL” can only mean that HCV RNA is detected.

A result of “<LLOQ, undetectable” or “<LLOQ target not detected”, or “less than LOD” are not technically possible since “<LLOQ” means HCV RNA has been detected. “Target Not Detected” and “<LLOQ” results are not the same.

All clinical trials for HCV DAAs have been conducted with the Roche High Pure (HPS/CTM HCV, v2.0) which has an LLOQ of 25 IU/mL and an LOD of 10-15 IU/mL, depending on genotype.1 However, to eliminate confusion, the CAP/CTM HCV test, v2.0 has an LLOQ and LOD equal to 15 IU/mL and is the test most commonly used for routine clinical practice and reporting of results.2

If your results are not reported as described above, please contact your laboratory for clarification.

Definition of terms

LLOQ

Lower limit of
quantification

The lowest concentration of HCV RNA
that can be accurately detected and
quantitated.
ULOQ

Upper limit of
quantification

The highest concentration of HCV RNA
that can be accurately detected and
quantitated.
LOD

Limit of detection

The lowest concentration of HCV RNA
that can be analytically detected 95% of
the time as required by the Food and
Drug Administration (FDA).

Reference:

1.
COBAS® TaqMan® HCV Test v2.0 for use with the High Pure System
2.
COBAS® AmpliPrep/COBAS® TaqMan® HCV Test, v2.0 [package insert]. Indianapolis, IN: Roche Diagnostics; 2014.