Nationwide Harmonization Effort for Semi-Quantitative Reporting of SARS-CoV-2 PCR Test Results in Belgium
Authors: Cuypers Lize , Bode Jannes , Beuselinck Kurt , Laenen Lies , Dewaele Klaas , Janssen Reile , Capron Arnaud , Lafort Yves , Paridaens Henry , Bearzatto Bertrand , Cauchie Mathieu , Huwart Aline , Degosserie Jonathan , Fagnart Olivier , Overmeire Yarah , Rouffiange Arlette , Vandecandelaere Ilse , Deffontaine Marine , Pilate Thomas , Yin Nicolas , Micalessi Isabel , Roisin Sandrine , Moons Veronique , Reynders Marijke , Steyaert Sophia , Henin Coralie , Lazarova Elena , Obbels Dagmar , Dufrasne François E. , Pirenne Hendri , Schepers Raf , Collin Anaëlle , Verhasselt Bruno , Gillet Laurent , Jonckheere Stijn , Van Lint Philippe , Van den Poel Bea , Van der Beken Yolien , Stojkovic Violeta , Garrino Maria-Grazia , Segers Hannah , Vos Kevin , Godefroid Maaike , Pede Valerie , Nollet Friedel , Claes Vincent , Verschraegen Inge , Bogaerts Pierre , Van Gysel Marjan , Leurs Judith , Saegeman Veroniek , Soetens Oriane , Vanhee Merijn , Schiettekatte Gilberte , Huyghe Evelyne , Martens Steven , Lemmens Ann , Nailis Heleen , Laffineur Kim , Steensels Deborah , Vanlaere Elke , Gras Jérémie , Roussel Gatien , Gijbels Koenraad , Boudewijns Michael , Sion Catherine , Achtergael Wim , Maurissen Wim , Iliano Luc , Chantrenne Marianne , Vanheule Geert , Flies Reinoud , Hougardy Nicolas , Berth Mario , Verbeke Vanessa , Morent Robin , Vankeerberghen Anne , Bontems Sébastien , Kehoe Kaat , Schallier Anneleen , Ho Giang , Bafort Kristof , Raymaekers Marijke , Pypen Yolande , Heinrichs Amelie , Schuermans Wim , Cuigniez Dominique , Lali Salah Eddine , Drieghe Stefanie , Ory Dieter , Le Mercier Marie , Van Laethem Kristel , Thoelen Inge , Vandamme Sarah , Mansoor Iqbal , Vael Carl , De Sloovere Maxime , Declerck Katrien , Dequeker Elisabeth , Desmet Stefanie , Maes Piet , Lagrou Katrien , André Emmanuel 
Published: June 2022

From early 2020, a high demand for SARS-CoV-2 tests was driven by several testing indications, including asymptomatic cases, resulting in the massive roll-out of PCR assays to combat the pandemic. Considering the dynamic of viral shedding during the course of infection, the demand to report cycle threshold (Ct) values rapidly emerged. As Ct values can be affected by a number of factors, we considered that harmonization of semi-quantitative PCR results across laboratories would avoid potential divergent interpretations, particularly in the absence of clinical or serological information. A proposal to harmonize reporting of test results was drafted by the National Reference Centre (NRC) UZ/KU Leuven, distinguishing four categories of positivity based on RNA copies/mL. Pre-quantified control material was shipped to 124 laboratories with instructions to setup a standard curve to define thresholds per assay. For each assay, the mean Ct value and corresponding standard deviation was calculated per target gene, for the three concentrations (107, 105 and 103 copies/mL) that determine the classification. The results of 17 assays are summarized. This harmonization effort allowed to ensure that all Belgian laboratories would report positive PCR results in the same semi-quantitative manner to clinicians and to the national database which feeds contact tracing interventions.