Experts say that the 2012 flu season is just starting, and although it is later than usual, they expect that about 5 million people will contract a severe form of flu that will claim 500,000 lives. Those most vulnerable are young children and older adults.

The important of fast diagnosis and treatment of flu is underlined in two research reports being published early online in Annals of Internal Medicine.

Receiving a correct diagnosis is vital to infection control and patient management for individuals who display flu-like symptoms, such as:

Viral cultures are accurate in diagnosing the flu, however, it can take up to 10 days to receive results from the lab. Newer tests called reverse transcriptase-polymerase chain reaction (RT-PCR) are significantly faster than viral cultures, although they require specialized equipment and are considerably costly, and rapid influenza diagnostic tests (RIDTs) are cheap and easy to use, although not much is known about their accuracy.

In the first study, a team of researchers set out to determine how accurate RIDTs are at diagnosing flu in children and adults displaying flu-like symptoms. The team examined 159 published studies in which RIDTs were tested against one or two approved reference standards.

The team discovered that although RIDTs were accurate at diagnosing the flu, they were not as precise at ruling it out. This means that individuals who received a negative result would require a follow up with a RT-PCR or culture. In addition, the team found that RIDTs were more accurate at detecting influenza virus A – which is more common – than influenza virus B, and that their sensitivity was around 13% higher in children than adults.

Results from the study indicate that RIDTs should be implemented in clinical practice, especially when treating patients at risk for flu-related complications and children.

Physicians may choose to start antiviral treatment when flu has been accurately diagnosed. In the second study, the researchers examined 74 published observational studies in order to determine the risks and benefits of 4 frequently prescribed antivirals: zanamivir, rimantadine, amantadine, and oseltamivir.

The researchers highlight evidence indicating that treating patients with antivirals within 48 hours may provide greater benefit than later treatment. They discovered that inhaled zanamivir and oral oseltamivir may provide a net benefit compared to individuals diagnosed with flu receiving no treatment.

Oral oseltamivir has been demonstrated to reduce the length of complications and symptoms from flu as well as mortality. The team found that on average, oseltamivir reduced patient symptoms by approximately 1 day compared to patients receiving no treatment. Furthermore, the team found that inhaled zanamivir could shorten the duration of flu and reduces signs and symptoms.

Written by Grace Rattue