Validation, implementation and quality control of a Torque Teno Virus qPCR in a multinational clinical trial

Immunosuppressive medication after organ transplantation is usually dosed through therapeutic drug monitoring. Trough levels of antirejection medication however, do not adequately predict rejection or infections. The TTVguideIT trial is a multinational clinical trial evaluating the safety of Torque Teno Virus (TTV) load assessed by qPCR, as an alternative to trough level tacrolimus dosing.

Prior to, and during the clinical trial, the inter-and intra-laboratory variability, accuracy, and precision of the TTV R-GENE® assay was evaluated through analysis of internal quality control (IQC), external quality assessment (EQA) and linearity panels performed by the thirteen participating clinical virology laboratories, each using their standard testing platforms.

IQC samples with a target of 4 log₁₀ copies/mL (cp/mL) were tested by the participating laboratories 130 times during the implementation phase and 987 times during the trial phase. They showed excellent accuracy, with an inter-laboratory standard deviation (SD) of 0.17 log₁₀ cp/mL, and an intra-laboratory SD of 0.03 to 0.20 log₁₀ cp/mL during the implementation phase, and an inter-laboratory SD of 0.19 log₁₀ cp/mL, and an intra-laboratory SD 0.07 to 0.18 log₁₀ cp/mL during the trial phase. Three EQA panels and three linearity panels showed similarly small variability during implementation as well as within the trial phase.

This data shows that TTV load measurement can be standardized for use in a multinational clinical trial. By using IQC, LP and EQA samples, the quality and integrity of the assay can be compared between laboratories and precise and accurate results can be generated.