MOLECULAR MICROBIOLOGY
2.0 2.5 3.0
0.0 0.5 1.0 1.5
12 10 8 6 4 2 0
Fig 2. Point-of-care GAS tests: rolling seven-day average. infection subsided,1 but it showed a
dramatic resurgence during the 2022–23 season. Its activity increased sharply early on and was described as a concern by the UK Health Security Agency (UKHSA). Data released showed that by week 46 there were 851 cases, compared to an average of 186 in preceding years.3
Although the
rise was seen in all age groups, the largest increases were observed in those under the age of 10. Zhi X et al.1
found that the M1UK
lineage represented 91% of invasive emm1 isolates in England in 2020, and during the 2022–2023 season emm1 strains accounted for >50% of invasive infections in children in England. The major factor for this was the COVID-19 pandemic restrictions. Children usually have their first episodes of scarlet fever in nursery or their early school years and gain immunity through repeated exposure. The restrictions put in place to reduce the spread of COVID-19 increased the age of first infection and
reduced the rates of re-exposure. It was widely acknowledged during the peak of last season that there were shortages of certain antibiotics (penicillin and amoxicillin). This was attributed to the fact that UKHSA issued new guidance enabling healthcare professionals to lower the threshold to prescribe antibiotics to children presenting with features of GAS infection.4
Paediatric consultant Dr Catherine
Hearnshaw, based at the Royal Derby Hospital, intended to trial the Abbott ID NOW, a molecular point-of-care (POC) test during the outbreak, the aim being to have a specific and sensitive method providing a faster result that could be used alongside a clinical algorithm to support antimicrobial stewardship.
Methodology The microbiology and the POC departments worked with paediatrics to determine the clinical value of the ID NOW Strep A POC test (Fig 3). Its use
was seen to be paramount in improving patient care as it is a rapid nucleic acid amplification test (NAAT) that provides results in six minutes or less, requiring a throat swab, and results transferred automatically to the patient’s electronic healthcare record (EHR).
Patients arriving in the paediatric
emergency department (ED) presenting with symptoms of pharyngitis followed clinical pathways and algorithms. In scenarios where patients would have a throat swab for traditional microbiology culture, they also had a throat swab to be tested on the ID NOW system. The authors compared 49 results between the ID NOW and the laboratory, including a timeline comparison. Furthermore, they compared the length of stay in ED during the verification and once the ID NOW had gone live, as well as reviewing antimicrobial prescribing for each patient.
Results
The ID NOW demonstrated that POC tests have a high sensitivity (100%), but specificity was lower (81%). Full details are shown in Figure 2 and Table 1.
Discussion and conclusions The authors demonstrated a far quicker diagnosis of GAS using ID NOW compared to traditional microbiology techniques. Alongside the algorithm put in place, they were able to rule out patients, therefore allowing patients to go home without the need for antibiotics. On reviewing antimicrobial
prescriptions within the dataset, it was clear that ID NOW helped maintain antimicrobial stewardship, with just 32% of patients receiving antibiotics during a time when the threshold for prescribing them was lowered by UKHSA.
Fig 3. The ID NOW Strep A POC test. 36
The ID NOW has successfully achieved the authors’ aims. It has demonstrated good sensitivity and specificity,
APRIL 2024
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Number of tests
19/12/2022 26/12/2022 02/01/2023 09/01/2023 16/01/2023 23/01/2023 30/01/2023 06/02/2023 13/02/2023 20/02/2023 27/02/2023 06/03/2023 13/03/2023 20/03/2023 27/03/2023 03/04/2023 10/04/2023 17/04/2023
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