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Abstract & Commentary
Validation of Self-Swabbing for Flu Infections in the Community
By Joseph F. John, MD, FACP, FIDSA, FSHEA, Associate Chief of Staff for Education, Ralph H. Johnson Veterans Administration Medical Center; Professor of Medicine, Medical University of South Carolina, Charleston, is Co-Editor for Infectious Disease Alert.
Dr. John reports no financial relationship to this field of study.
Source: Ip DKM, et al. Validation of self-swab for virologic confirmation of influenza virus infections in a community setting. J Infect Dis 2012;205:6314.
Hong Kong investigators conducted 2 separate community studies using careful face-to-face instructions to potentially influenza infected patients. Sterile nasal swabs were rotated around the anterior nares. The throat culture was the sample collected by "rubbing a second sterile swab against the tonsillar fossa." Reverse-transcription polymerase chain reactions (RT-PCR) was used to find and quantitate both influenza A and influenza B particles expressed as viral particles per milliliter. There were 109 of 121 (90%) of positive patients who had detectable virus within the first 2-5 days after onset of symptoms. Virus quantity for influenza A tended to start to decline from highs of 108 particles down to 104–102 by day 8 or 9. Influenza B levels tended to be a log or 2 lower.
This study shows that patients are quite capable of swabbing their own nose and throat in order to find adequate RNA specific for influenza A and B viruses. In fact the viral loads were relatively huge at the outset of disease suggesting that the authors used an excellent method for transport and preservation. In the study of household transmission, in fact, the initial viral loads approached 1010!
If we use www.Googlescholar.com to search self swabbing and cultures, there are 18,600 hits. So the field of self culturing is rich and getting richer. It seems that vaginal swabs have been studied most followed by throat, nasal and ultimately rectal.
The use of the swab itself for microbial culture, emerged around 1940, but a battle raged about whether a primary specimen like feces was preferable to rectal swabs. Back in the August 14, 1954, issue of the British Medical Journal, rectal swabs were compared to feces as a method for detecting enteric pathogens. Swabs were found to be wanting (MEM Thomas, "Disadvantages of the rectal swab in diagnosis of diarrhea").
Swab science, however, has markedly improved into the modern age, as suggested by the excellent recovery of RNA — even by self swabbing — in the current report by Ip, et al. In fact, self-collected swabs were compared for accuracy to ones obtained by health care professionals and no difference was present.
This study is the first to measure recovery of influenza virus by self swabbing. The findings are quite astounding and show that rapid sampling of the populations at large is quite feasible using self swabs, hopeful indeed that those populations can be as assiduous in sample collection as these residents of Hong Kong. Other community-based populations should be studied but this report serves as a trigger to suggest the use of a careful nose or throat swab and subsequent careful transport to the clinical virology laboratory may allow for rapid diagnosis, infection control and therapy of influenza epidemics.