Apropos ‘performance of influenza point‐of‐care tests in the detection of pandemic (H1N1) 2009 influenza viruses’

Abstract

To the Editor: We write to support Hurt et al.1 regarding the urgent necessity of point-of-care (POC) test kits with enhanced sensitivity for influenza diagnosis. Recent evaluations of three POC tests, the Binax Now, BD, Directigen EZ and Quidel Quick Vue, with stock viruses and clinical specimens have been enlightening. Although at high virus concentration they matched real-time RT-PCR results when employing Swine lineage A (H1N1) and human seasonal influenza strains, they performed poorly in samples with low virus concentration.1 That was also observed in the USA during April–May 2009 with 65 clinical respiratory samples. POC kits did detect Swine lineage A (H1N1) in those samples that had high levels of virus, as indicated by low cycle threshold in real-time RT-PCR.2 Funds should be spared for research in biotechnology towards novel influenza (A H1N1) antigen detection kits for universal use in health care centers and particularly in laboratories with minimum infrastructure. Fiscal support would be cost effective and strengthen innumerable resource-poor laboratories where virus culture, shell vial culture, direct immunofluorescence or real-time RT-PCR is not feasible. Lack of competent diagnostic laboratories in poor countries has been alarming in rural and remote areas and even in urban areas.3 Detection kits would be beneficial only if their sensitivity was better than the existing locally available POC kits. Furthermore, the cost of POC kits needs to be reduced at least for the laboratories in resource poor countries. International funding organizations should prevail upon the manufacturers to introduce a differential cost for such kits in resource poor countries. Most of the current kits detect only influenza A and B and do not differentiate between influenza subtypes. Incorporation of extra monoclonals into future POC kits should enable sub-typing of influenza strains on the test strip itself. Enhanced sensitivity and specificity apart, future POC kits should be environmentally robust to handle unpredictable field rigors in different continents. The new ‘lab on a chip’ technology that would rely on a handheld device for a quick and inexpensive DNA testing is fascinating. The results would not be read by the human eye but recorded on the hand-held device itself. With ‘lab on a chip’ quick turn around time immediate on site diagnosis and treatment could be a reality without the need for a complex and expensive laboratory.4 Clearly ‘lab on chip’ technology of increased sensitivity and specificity would be of immense value even in resource poor countries. Last but not least, improved versions of influenza POC kits for clinical diagnosis of pandemic (H1N1) 2009 influenza virus1 would be valuable during phase 1, 2 and 3 or subsequent trials with prospective vaccines. None. None. Not required.