Pertussis, commonly known as ‘whooping cough’, is a highly contagious infection of the respiratory tract caused by the bacterium Bordetella pertussis. Infants <6 months of age are at the greatest risk of severe disease and death. Pertussis is included as part of the childhood immunisation schedule https://beta.health.gov.au/resources/publications/national-immunisation-program-schedule-portrait.

ClinicalThe clinical diagnosis of pertussis is based on a cough illness lasting ≥2 weeks with coughing paroxysms, inspiratory “whoop”, or post-tussive vomiting, without another apparent cause.

Laboratory DiagnosisThe laboratory diagnosis of pertussis is important for both individual patient management and public health responses. Pertussis may be diagnosed by culture or nucleic acid amplification (PCR) of the pathogen in appropriate specimens, and/or by the demonstration of a Bordetella pertussis toxin (BPT) specific antibody response.

Culture of B. pertussis from clinical specimens is no longer routinely performed. Nucleic acid amplification techniques, principally by the polymerase chain reaction (PCR), is now the main method of diagnosis for acute pertussis. PCR is significantly more sensitive and rapid than culture and has become the ‘gold standard’. It is less affected by antibiotic therapy and remains positive for longer in the course of the illness. Although nasopharygeal swabs are preferable, throat swabs are also acceptable for PCR; a significant advantage for testing older children and adults. In our collection rooms both nasopharyngeal swabs and throat swabs are collected and the two specimens combined for testing.

Serology is also used to diagnose pertussis utilizing the detection of a specific antibody response. The literature and our own publications suggest elevated BPT IgG results ≥ 100 IU/mL correlate well with recent infection. Results are now reported using international units referenced to the WHO International Standard. BPT IgG responses decline fairly rapidly and BPT IgG is usually <100 IU/mL within one year post infection. Its presence in well and mostly vaccinated children is <3%. Many variables can however affect these antibody levels including prior infection, and vaccination.

Pertussis Sullivan Nicolaides Pathology

The choice of investigations is principally determined by the clinical stage of the illness.

Duration of Symptoms (cough onset)

Recommended Test Recommended Specimens

0-2 weeks PCR Combined nasopharyngeal flocked swab and throat swab. Throat swab may be used for PCR although the sensitivity is likely to be slightly reduced

2-4 weeks PCR and Serology As above plus serum

>4 weeks Pertussis toxin IgG (BPT IgG) Serum

This report contains summary data for testing at Sullivan Nicolaides Pathology based on results of molecular testing (PCR) and Serology (BPTIgG).

Pertussis PCR results 1. All pertussis PCR tests (reported as positive and negative) by week and current year.2. All positive pertussis PCR results by age, sex and current year.3. All pertussis and positive pertussis PCR testing by year from 2004 to current year.4. All positive pertussis PCR tests by state for current year.5. All positive pertussis PCR results by age and year.

Pertussis Serology results 6. All Bordetella pertussis Toxin (BPT) IgG results by week and current year. (Positive - BPT IgG >100 IU/mL; Equivocal - BPT IgG 60 - 100 IU/mL; Negative - BPT IgG < 60 IU/mL)7. All serologically diagnosed cases of acute pertussis; defined as the first episode of BPT IgG >100 IU/mL in the previous 12 months. 8. All new serologically diagnosed pertussis PCR results by age, sex and current year.

Pertussis Combined PCR and Serological Diagnoses9. All cases of serological + PCR diagnosed cases by week and current year.10. All cases of serological + PCR diagnosed cases by year.

Page: 1

Page: 2

5. All positive pertussis PCR results by age and year.

4. All positive pertussis PCR tests by state for year 2019. This represents testing done by SNP only. A more complete national picture can be found at http://www9.health.gov.au/cda/source/rpt_4.cfm.

Page: 3

Page: 4

References:May ML, Doi S, King D, Evans J and Robson J A Prospective Evaluation of an Australian Pertussis Toxin IgG and IgA Enzyme Immunoassay" Clinical Vaccine and Immunology 2012;19:190-7.May ML, Evans J, Holgate T, Doi SA, Ross P, Robson JM. Pertussis toxin IgA testing over-diagnoses recent pertussis infection. Pathology. 2017 Dec 1;49(7):770-5.

@Sullivan Nicolaides Pathology (2019). If you wish to use this report or any data or graphs contained in the report you must seek the written permission of Sullivan Nicolaides Pathology. To request permission please send the following details and assurances to Marketing@snp.com.au

How the work will be used? Will the work be adapted? If it will be adapted or changed in any way, give specific details of the changes. Will it be included within other content, and if so what is the overall context, and what proportion of the overall work

does the copied content represent. An assurance that the work will be properly attributed and will not be falsely attributed.

Page: 5