Misdiagnosis of H1N1 Influenza Cases

During the April-July 2009 outbreak of H1N1/2009 in scotland the West of Scotland Specialist Virology Centre (WoSSVC) in Glasgow tested more than 16 000 clinical samples for H1N1/2009. Most were from patients clinically diagnosed with H1N1/2009. Out of these, 9 percent were positive. Rory N Gunson and William F Carman of Gartnavel General Hospital in Glasgow, Scotland, sought to determine what respiratory pathogens were misdiagnosed as cases of H1N1/2009 during this time.

The researchers examined the results from 3,247 samples which were sent to the laboratory during April-July 2009. All were from patients clinically diagnosed as having H1N1/2009 (based on accepted criteria) and all were given a full respiratory screen using real time reverse transcriptase polymerase chain reaction (rtRT-PCR) assays.

In total, respiratory pathogens were detected in 27.9 percent (95% confidence interval, 26.3-29.5%) of the samples submitted. Numerous pathogens were detected, the most common of which were rhinovirus (8.9 percent (95% confidence interval, 7.9-9.9%)), parainfluenza 1 (1.9% (95% confidence interval, 1.4-2.4%)) and 3 (4.1% (95% confidence interval, 3.3-4.9%)), and adenovirus ((3.5 percent (95% confidence interval, 2.9-4.2%)).

This study highlights the problems of using a clinical algorithm to detect H1N1/2009. Clinicians frequently misdiagnosed common respiratory pathogens as H1N1/2009 during the spring/summer outbreak in Scotland. The researchers say that many undesirable consequences would have resulted, relating to treatment, infection control, and public health surveillance. Their research was published in BMC Infectious Diseases.

Reference: Gunson RN and Carman WF. During the summer 2009 outbreak of "swine flu" in Scotland what respiratory pathogens were diagnosed as H1N1/2009? BMC Infectious Diseases 2011, 11:192doi:10.1186/1471-2334-11-192