Difficulty in the Rapid Diagnosis of Avian Influenza A Infection: Thailand Experience

Anucha Apisarnthanarak, Rungrueng Kitphati, and Linda M. Mundy


TO THE EDITOR—We would like to report our experience with the use of rapid tests for confirmation of avian influenza A (H5N1) infection in Thailand. During the first H5N1 infection outbreak in Thailand (1 December 2003 to 31 March 2004), nasopharyngeal specimens from 610 patients (range, 1–3 specimens per patient) were submitted to the Thai National Institute of Health [1, 2]. Twelve (2%) of 610 patients had confirmed H5N1 infection by RT-PCR, real-time RT-PCR, and/or viral culture results. Of these 12 patients, 7 (58%) had specimens submitted for nasopharyngeal rapid testing; 2 (28.5%) of these 7 patients had nasopharyngeal rapid test results positive for H5N1 (SD Bioline Influenza Antigen A/B [MT Promedt Consulting] and Quickvue Influenza A+B test [Quidel]). Quality-improvement initiatives identified inappropriate specimen procurement, incorrect specimen containment, or delayed specimen shipment for 4.8% of the nasopharyngeal specimens obtained. A county-wide educational program on proper specimen procurement, transport, and processing occurred from 1 April through 31 August 2004. After the educational program, 4417 patients had at least 1 specimen (range, 1–6 specimens per patient) submitted for H5N1 testing. There was a notable reduction in suboptimal specimen collections to 2.4% (P = .02). Thirteen (0.3%) of 4417 patients had H5N1 infection confirmed by RT-PCR, real-time RT-PCR, and/or viral culture results. Ten (77%) of these 13 patients had specimens submitted for nasopharyngeal rapid testing, and 3 (30%) of these 10 patients had nasopharyngeal rapid test results positive for H5N1. Of note, 1 patient with H5N1 infection received neuraminidase inhibitor >48 h before specimen collection and had negative nasopharyngeal rapid test results.

Our findings have some important implications. Although physicians tend to submit multiple specimens from each index patient, and although suboptimal specimen collection and processing were identified less commonly after the educational program, we found no difference in the diagnostic yield of the rapid test. With the increase in neuraminidase inhibitor supply in Thailand, physicians tend to prescribe this medication to the index patient long before specimen collection. Because rapid diagnosis for H5N1 infection can be difficult [3], we emphasize the importance of treating physicians obtaining multiple adequate, deep specimens from patients before the administration of antiviral medication to the index patient.

Acknowledgments

Potential conflicts of interest. All authors: no conflicts.

References
1. Chotpitayasunondh T, Ungchusak K, Hanshaoworakul W, et al. Human diseases from influenza A (H5N1), Thailand, 2004. Emerg Infect Dis 2005; 11:201–9. First citation in article | PubMed
2. Thai National Institute of Health. Coordinating Center for Laboratory Testing and Surveillance. Available at: http://www.cclts.org/UPDATE/page.html. Accessed 18 December 2006. First citation in article
3. Oner AF, Bay A, Arslan S, et al. Avian influenza A (H5N1) infection in east Turkey in 2006. N Engl J Med 2006; 355:2179–85.