Interpreting newer rapid influenza tests in Australian hospitals

Hospital Medicine 2017 brought hospitalists and other healthcare professionals together at Mandalay Bay Resort and Casino in Las Vegas, Nevada, from 1 to 4 May. Organised by the Society of Hospital Medicine, the meeting combined research, practical education and continuing medical education credits with professional networking. Its most useful lessons connect laboratory science to bedside decisions about prescribing, infection prevention and discharge.

One programme item was “The Hospitalist’s Guide to Interpreting Newer Rapid Influenza Tests: HM17 Session.” For Australian clinicians, its focus remains relevant as seasonal surges pressure emergency departments and acute medical units. Rapid results can shorten the interval between suspicion and action, but speed does not remove uncertainty. A useful interpretation links assay performance, pre-test probability and the decisions that should follow.

Interpretation depends on three layers: the assay, the patient and the service around them. Antigen lateral-flow tests detect viral protein, while newer point-of-care molecular tests detect nucleic acid and may include other respiratory targets. Neither category is a universal answer. In Australia, the Therapeutic Goods Administration regulates the device market, accredited pathology services work under National Association of Testing Authorities standards, and point-of-care programmes need local governance matched to their intended use.

Why a rapid result needs clinical context

Conference resources are available through the HM17 conference portal. The practical differences become useful when each assay is matched to its intended use:

Pre-test probability changes the meaning of every result. During a documented influenza surge in Melbourne or Sydney, a compatible positive antigen test is more likely to be true. Outside that setting, an unexpected positive deserves review. In low-prevalence periods, false-positive results can form a larger share of positives. Hospitalists should record why they ordered the test and what result would alter management.

Sample quality and timing are equally important. Nasopharyngeal or combined nasal-throat swabs must be collected as directed, and a poorly handled specimen can invalidate an otherwise reliable assay. Antigen sensitivity often declines after several days of symptoms, making a negative result less reassuring in late-presenting pneumonia. A molecular test can remain positive after infectious virus has cleared, so detection should not be equated automatically with transmissibility.

Reading newer rapid tests at the bedside

Molecular results require careful wording. A nucleic-acid amplification test can identify influenza A or B and, depending on the panel, distinguish subtypes or detect other viruses such as RSV. A detected target supports the diagnosis, but it does not estimate infectiousness. If the report includes a cycle threshold, clinicians should not translate it into viral load, severity or duration of illness; those interpretations require a validated assay and clinical context.

When a rapid result disagrees with the clinical picture, the response should be deliberate rather than automatic. Consider repeating the test with a freshly collected specimen, checking whether the laboratory can provide confirmatory nucleic-acid testing and reviewing complications that might explain prolonged or atypical symptoms. A negative antigen test in a high-risk patient should not end diagnostic thinking if influenza remains clinically plausible.

Quality failures can masquerade as negative or positive results. Internal controls, reagent storage, lot tracking, operator competency and external quality assurance should be reviewed after an invalid, indeterminate or discordant result. Before acting, clinicians should confirm that the correct test was used, understand the device instructions and arrange confirmatory testing where required.

Applying tests during an Australian winter

Influenza activity in southern cities such as Melbourne and Sydney usually peaks from June to September, while Cairns and Darwin experience more year-round circulation. Many Australians manage early symptoms at home, seek advice from a GP or community pharmacist, or attend an emergency department when breathlessness, dehydration or deterioration develops. A testing pathway must therefore bridge primary care, pharmacy, emergency care and the inpatient team rather than assume one route.

Before the test:

• Record symptom onset, vaccination status, relevant contacts and recent travel.
• Use the specimen and operator steps specified in the device instructions.
• Check controls, reagent storage and staff competency before testing.
• Apply locally recommended infection-control precautions while the result is pending.

When the result returns:

• Match the result with symptoms, age, comorbidities and local influenza activity.
• Verify that the run is valid and review any error or indeterminate message.
• Record antiviral, isolation and notification actions in the clinical note.
• Escalate clinical deterioration immediately rather than waiting for another test.

Follow-up should also cross the care boundary. A patient discharged from an Australian emergency department with suspected influenza may return to a GP or community pharmacy, so written instructions should identify the treating team, medication plan, worsening symptoms and who will review a confirmatory result.

Converting results into treatment and isolation

Results should influence treatment rather than merely end a testing episode. Prompt antiviral treatment, usually oseltamivir, is strongly indicated for severe or progressive disease and for patients at high risk of complications; it should not be delayed for confirmation when the clinical indication is clear. Eligible outpatient use is shaped by Pharmaceutical Benefits Scheme criteria, while admitted patients generally receive medicines through the hospital formulary.

Infection prevention should move in parallel. Local policy generally calls for standard precautions plus droplet precautions for suspected influenza, with enhanced protection for aerosol-generating procedures where indicated. Isolation and personal protective equipment should not wait for a molecular result. Confirmed influenza is nationally notifiable, but the exact pathway differs by state and territory. A positive molecular result may be laboratory-notifiable, while an antigen result may require confirmation under local rules.

The same conference archive includes a hyponatraemia protocol review, illustrating a broader hospital-medicine principle: diagnostic information matters when it is attached to a threshold, an accountable clinician and a documented response. Influenza results need the same operational structure.

Building a reliable hospital-wide pathway

A dependable hospital-wide pathway assigns ownership before the season begins. The order set should identify the test type, specimen requirements and where confirmatory testing will occur. Staff need a defined route for reviewing positives, ordering confirmation, documenting antiviral treatment, checking isolation and completing notification. Electronic results should reach a named clinician rather than disappear in an inbox.

Performance should be audited by site and season. Turnaround time, invalid rates, discordance, time from result to treatment and isolation, and notification timeliness reveal where the process fails. Metropolitan hospitals may have around-the-clock molecular testing, while regional services may depend on courier transport or a validated point-of-care pathway. Telehealth and remote review can support those sites while preserving the same clinical standard.

Patient communication is part of test interpretation. Plain-English explanations should distinguish a screening result from a confirmed diagnosis, explain which medicines were prescribed and provide safety-net advice. People leaving hospital often lack laboratory confirmation and may be managed in the community, so the hospital should send relevant results and instructions to the GP and provide a contact for deterioration.

Turning the session into daily practice

Reliable interpretation combines analytical performance with clinical probability and a service response. Before acting on a result, ask what the assay detects, whether the specimen and timing are appropriate and which decision the result can safely change.

The HM17 session remains a useful guide to that reasoning, but current Australian guidance, device instructions and local protocols should take precedence as molecular testing availability and hospital formularies evolve.

At the next hospital governance meeting, add one line to the influenza pathway: every positive rapid result receives a documented hospitalist review within 30 minutes, with named ownership for antiviral treatment, isolation and public-health notification.