On the contribution of diagnostic testing to health maintenance and health care
Friday, May 15, 2009
In preparation for the Fall
As the number of confirmed cases seems to be decreasing (as shown by the May 4th CDC figure) and severity appears not to exceed that of seasonal influenza, public attention to the 2009 H1N1 flu wanes. Laboratorian's attention should not: as mentioned earlier, parallels with the 1918 pandemic predict worse outbreaks in the Fall. In my opinion, the following laboratory diagnostic tools should be in place in the U.S. by then: (1) a sensitive molecular test for virus detection and (2) a specific serum/plasma antibody test for retroactive diagnosis.
The CDC developed the amplified RNA test in an amazingly short time. However, it has been limited to local Public Health laboratories. Despite those laboratories' heroic efforts, this limitation precludes its widespread use. The first test offered outside Public Health labs, was only made available by Quest Diagnostics two days ago. However, this test is only offered in one location in the U.S. and still requires confirmation by local Public Health laboratories. Further, important details of sample collection and estimates for the clinical sensitivity of the molecular test are not yet available.
I was personally involved in two potential school events which begged a rapid sensitive test. I described the first experience below (another teacher in that school's district has since been confirmed as suffering from the swine flu). Last Friday, I was asked advice in a third-grade incidence, where six out of 30 students in a single classroom in a school in New York City fell ill with suggestive symptoms. On Monday half of the students in the class, including five of the six, were absent. The symptoms (fever, malaise, headache, muscle aches) of the sixth, a nine year old girl whose pediatrician prescribed Tamiflu (oseltamivir) on Saturday, resolved within hours of starting treatment. Today, a week later, most of the sick children have returned, and the whole class is visiting the local Zoo. If the incident was, in fact, due to the flu, this group of students has disseminated the virus widely. Had one of the sick students been tested within the first day and found to host the H1N1 virus, the school might have decided to take containing measures, including possible closure, despite the CDC advise of not to close "unless there is a magnitude of faculty or student absenteeism that interferes with the school's ... ability to function."
While we should no longer worry that the children who fell ill last week could spread the virus, others in the incubation phase of this potential H1N1 outbreak, might. In this scenario, the finding of specific antibodies in the blood of convalescent students, could help with containment efforts and in the diagnosis of contacts. Such antibody test would also be used as an important epidemiological tool.