Case definition and clinical testing guidelines for COVID-19

Case definition and clinical testing guidelines for health practitioners

Page updated 7 May 2021

Summary of changes: 7 May
The content of this page has been substantially changed and information updated. The Higher Index of Suspicion criteria have been updated to reflect new quarantine free travel arrangements.

This page provides guidance to support health professionals to identify and test those individuals who may have a higher risk of having COVID-19. It includes clinical criteria of COVID-19, the Higher Index of Suspicion (HIS) criteria, case definitions and notification procedures.

For more information on testing refer to: the COVID-19 Testing Plan, which outlines a systematic risk-based approach to testing at the border, in the community, and for containment or cluster management purposes; and Testing Guidance for the Health Sector, which contains more detailed advice that will be regularly updated to take into account New Zealand’s current situation including COVID-19 Alert Level status.

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Guidelines for testing

People should be tested who have symptoms that meet the clinical criteria for COVID-19 (detailed below). 

Where people meet the clinical criteria for COVID-19 and also meet the HIS criteria (outlined on page 2), extra steps (self-isolation and notification) are needed.

People may also be tested when they are asymptomatic and:

  • they are required to undertake mandatory routine testing at specified intervals (e.g., border and MIQ workers),
  • they are contacts of confirmed (or probable) cases. 

For definitions and guidance on management of contacts (e.g. Close Plus, Close, Casual Plus and Casual Contacts) see Contact tracing.

Clinical criteria for COVID-19

The following symptoms are consistent with COVID-19.

Any acute respiratory infection with at least one of the following symptoms (with or without fever): 

  • new or worsening cough,
  • fever (at least 38˚C),
  • shortness of breath,
  • sore throat,
  • coryza (runny nose),
  • anosmia (loss of sense of smell),
  • dysgeusia (altered sense of taste).

People meeting the clinical criteria for COVID-19 should be tested. Some people may present with less typical symptoms such as only fever, diarrhoea, headache, myalgia (muscle aches), nausea/vomiting, or confusion/irritability. For people with less typical symptoms, if there is not another more likely diagnosis, they should also be tested.

Other conditions that require urgent assessment and management should always be considered as possible diagnoses alongside COVID-19.

Higher Index of Suspicion (HIS) criteria

People who meet the HIS criteria are those who have, in the 14 days prior to symptom onset:  

  • travelled internationally (excluding travel by air from a country/area with which New Zealand has quarantine-free travel (QFT)*),
  • had direct contact with a person who has travelled internationally in the preceding 14 days (excluding travel by air from a QFT country/area). e.g. Customs and Immigration staff, staff at quarantine/isolation facilities,
  • exited an MIQ facility (excluding recovered COVID-19 cases),
  • worked on an international aircraft or shipping vessel (excluding aircraft from a QFT country/area), 
  • cleaned at an international airport or maritime port in areas/conveniences visited by international arrivals (excluding areas/conveniences for travellers by air from a QFT country/area), 
  • worked in cold storage areas of facilities that receive imported chilled and frozen goods directly from an international airport or maritime port, or 
  • any other criteria requested by the local Medical Officer of Health. 

*a list of QFT countries/areas can be found on the Unite Against COVID-19 website. QFT only refers to travel by air at this point. 

People meeting the HIS criteria who also meet the clinical criteria for COVID-19 (a HIS person) should be tested for COVID-19 and self-isolate while awaiting test results to reduce the risk to others. Notification of the HIS person needs to be made to local Medical Officer of Health.

Case classification

Under investigation case

A case that has been notified where information is not yet available to classify it as confirmed, probable or not a case. 

Probable case

  • A close contact of a confirmed case that has a high exposure history, meets the clinical criteria and for whom testing cannot be performed, or
  • A close contact of a confirmed case that has a high exposure history, meets the clinical criteria, and has a negative PCR result but it has been more than 7 days since symptom onset before their first negative PCR test was taken.

Confirmed case

A case that has laboratory definitive evidence. Laboratory definitive evidence requires at least one of the following:

  • detection of SARS-CoV-2 from a clinical specimen using a validated NAAT (PCR). Very weak positive results will only be labelled a confirmed case when the result is confirmed on a second sample.
  • detection of coronavirus from a clinical specimen using pan-coronavirus NAAT (PCR) and confirmation as SARS-CoV-2 by sequencing
  • significant rise in IgG antibody level to SARS-CoV-2 between paired sera.

Not a case

An ‘under investigation’ case who:

  • has a negative test and has been assessed as not a case;
  • a person where SARS-CoV-2 has been detected where the detection is determined to be due to a previous COVID-19 infection which has already been recorded either in New Zealand or overseas; 
  • a person who has detection of SARS-CoV-2 from a clinical specimen but, following further investigations such as serology, repeat testing, history and symptoms, they are deemed to not be a case (e.g. a likely false positive).

Historical case 

A confirmed case that is deemed to have recovered (no longer considered infectious) at the time of testing. 

Notification procedure

Laboratories must immediately notify the local Medical Officer of Health of any confirmed cases.

Attending medical practitioners must notify the local Medical Officer of Health of any confirmed cases, people they believe may be probable cases AND anyone who meets both the clinical and HIS criteria (notification should include the symptoms meeting the clinical criteria and how the HIS person meets the HIS criteria).

 

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