An understanding of discordant SARS-CoV-2 test results: An examination of the data from a central Auckland laboratory

AIM: The diagnostic sensitivity of the SARS-CoV-2 real time reverse transcription polymerase chain reaction (RT-PCR) test has not been determined. This has led to a degree of uncertainty in the interpretation of results, particularly in patients tested repeatedly. The aim of this study was to explore the characteristics of patients who initially tested negative, and subsequently tested positive for SARS-CoV-2. METHOD(S): This retrospective observational study utilised data from the LabPlus Virology laboratory, Auckland City Hospital, to identify cases (hospital and community) with initial negative and subsequent positive SARS-CoV-2 RT-PCR results. Their clinical and laboratory characteristics were summarised. RESULT(S): From 1 February to 13 April a total of 20,089 samples were received for SARS-CoV-2 testing. Of 2,011 samples from patients with multiple tests, 25 samples were positive. Nine samples were from patients who initially tested negative then tested positive. Reasons for the initial negative test results, which were all from upper respiratory tract samples, included pre-symptomatic presentation or late presentation. All patients had significant risk factors and ongoing or evolving symptoms, which warranted repeat testing. CONCLUSION(S): Few patients had discordant test results for SARS-CoV-2 RT-PCR. For patients who have a significant risk factor and a negative test result, repeat testing should be performed. Copyright © 2020 New Zealand Medical Association. All rights reserved.

Age-related differences in SARS-CoV-2 testing in the Northern Region of New Zealand

AIM: There is concern the low incidence of coronavirus disease 2019 (COVID-19) in children reflects undertesting in this population. This study sought to describe the age-distribution of SARS-CoV-2 testing in the Northern Region of New Zealand. METHODS: A retrospective single-centre review of all SARS-CoV-2 tests performed at LabPLUS, Auckland City Hospital, between 12 February and 18 April 2020. RESULTS: A total of 22,333 tests were performed, with 313 (1.40%) positive results. The age-adjusted SARS-CoV-2 testing rate was three times higher in adults than in children. The overall proportion of positive tests was lower in children (0.86%) than adults (1.45%). However, within the paediatric population the proportion of tests positive differed significantly between those <10 years old (0.08%) and those 10-14 years old (2.6%). CONCLUSION: The lower proportion of tests positive in children <10 years of age suggests they are appropriately tested relative to their rates of disease. A large high school-associated cluster makes the higher proportion of tests positive in children 10-14 years old difficult to interpret. Older children may have a higher risk of infection and increasing testing in intermediate and high school aged children may be indicated. © 2020 New Zealand Medical Association. All rights reserved.

An understanding of discordant SARS-CoV-2 test results: an examination of the data from a central Auckland laboratory

AIM: The diagnostic sensitivity of the SARS-CoV-2 real time reverse transcription polymerase chain reaction (RT-PCR) test has not been determined. This has led to a degree of uncertainty in the interpretation of results, particularly in patients tested repeatedly. The aim of this study was to explore the characteristics of patients who initially tested negative, and subsequently tested positive for SARS-CoV-2. METHODS: This retrospective observational study utilised data from the LabPlus Virology laboratory, Auckland City Hospital, to identify cases (hospital and community) with initial negative and subsequent positive SARS-CoV-2 RT-PCR results. Their clinical and laboratory characteristics were summarised. RESULTS: From 1 February to 13 April a total of 20,089 samples were received for SARS-CoV-2 testing. Of 2,011 samples from patients with multiple tests, 25 samples were positive. Nine samples were from patients who initially tested negative then tested positive. Reasons for the initial negative test results, which were all from upper respiratory tract samples, included pre-symptomatic presentation or late presentation. All patients had significant risk factors and ongoing or evolving symptoms, which warranted repeat testing. CONCLUSION: Few patients had discordant test results for SARS-CoV-2 RT-PCR. For patients who have a significant risk factor and a negative test result, repeat testing should be performed.

Age-related differences in SARS-CoV-2 testing in the Northern Region of New Zealand

AIM: There is concern the low incidence of coronavirus disease 2019 (COVID-19) in children reflects undertesting in this population. This study sought to describe the age-distribution of SARS-CoV-2 testing in the Northern Region of New Zealand. METHODS: A retrospective single-centre review of all SARS-CoV-2 tests performed at LabPLUS, Auckland City Hospital, between 12 February and 18 April 2020. RESULTS: A total of 22,333 tests were performed, with 313 (1.40%) positive results. The age-adjusted SARS-CoV-2 testing rate was three times higher in adults than in children. The overall proportion of positive tests was lower in children (0.86%) than adults (1.45%). However, within the paediatric population the proportion of tests positive differed significantly between those <10 years old (0.08%) and those 10-14 years old (2.6%). CONCLUSION: The lower proportion of tests positive in children <10 years of age suggests they are appropriately tested relative to their rates of disease. A large high school-associated cluster makes the higher proportion of tests positive in children 10-14 years old difficult to interpret. Older children may have a higher risk of infection and increasing testing in intermediate and high school aged children may be indicated.