Feb 8, 2022

Defining and reporting on critical values in genetics

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As part of an initiative to harmonize critical value reporting across genetic laboratories in the Greater Toronto Area (GTA), we sent a survey of 11 questions via email to genetic laboratory directors in Ontario in July 2019 and also September to October 2019 since there was a paucity of data for critical values in genetics.

Based on the data, the Council formulated proposed guidelines that were circulated to individuals from Ontariogenetic laboratory centres and respondents of the survey in November 2021, who supplied feedback.

We recommend all genetic laboratories consider implementing these guidelines into their critical value reporting.

Please supply any feedback on the guidelines or their implementation to Dr. Elaine Goh.

Critical patient type

  • Prenatal
  • Newborn
  • Oncology or
  • Expedited by the ordering physician

Critical results

  • Cytogenetics: Prenatal abnormal rapid aneuploidy testing or microarray findings
  • Molecular: Unexpected results, and pathogenic variants in prenatal setting (Indeterminate results taken off after feedback from Ontario genetic laboratory centres).

Reporting process

  • Insufficient or incorrectly labelled samples: Do not limit to reporting via mail
  • Critical results: Suggest in addition to routine process to either also call, email and/or fax the ordering provider.

Other resources on this topic

Authors / contact

Compiled by

Dr. Elaine Goh
Assistant Professor, Department of LaboratoryMedicine and Pathobiology, University of Toronto
Division Head of Clinical Genetics, Trillium Health Partners



Dr. James Stavropoulos
Assistant Professor, Department of Laboratory Medicine and Pathobiology, University of Toronto and Clinical Lab Director of Genetics at The Hospital for Sick Children

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