By Travis Jobe, Senior Specialist, Laboratory Systems & Standards – Vaccine-Preventable Diseases, APHL
So where do the public health labs enter the story on measles?
One of the key components for identifying measles cases is laboratory diagnostics. This can be especially important when immunized persons become sick with measles but don’t present with typical symptoms due to their partial immunity. However, the limited number of assays available to public health laboratories for measles diagnostics limits their abilities to detect the disease. Also, because a laboratory rarely gets a chance to run the test on real cases, it may be hard to be confident in any given assay’s performance. The APHL Recovery Act-funded Vaccine-Preventable Diseases (VPD) project has attempted to confront the question of performance of measles serology assays by offering public health laboratories the opportunity to participate in a pilot proficiency testing-like exercise. Anyone who hasn’t worked in a diagnostic laboratory probably doesn’t know what proficiency testing, or PT, is. But, essentially, PT is a panel of positive and negative samples sent to a laboratory to test and see if they get the correct results. PT is a vital part of the work that public health laboratories perform to assure that they are competent in the results they report – results that impact the treatment of people like you and me.
Thirty-five public health laboratories from 30 different states participated in this measles serology PT exercise. As it turns out, the results did point out some variances in the assays public health laboratories use for measles serology testing. It just goes to show that not all assays may work perfectly for laboratory diagnosis, which shouldn’t be news to anyone in the medical or public health field. But as long as the laboratorians themselves know about and understand these limitations, the proper interpretation of laboratory results can be communicated to the epidemiologists and doctors who are confronting the measles cases – real patients – directly. Travelers with measles continue to return to the US this year from Europe and other areas of the world with ongoing measles outbreaks. The laboratories that participated in the PT exercise are already putting to use this increased knowledge of their assays’ performance as they are called upon to perform the testing for these cases. This includes the public health laboratories of Minnesota, California, New York, Pennsylvania, Washington, Texas, Florida, New Mexico, and New Jersey – just to name a few of the states that have seen imported measles this year.
For the general public, not only does the public health response prevent further illness by limiting disease transmission, it also helps to save further expenses – real money. In the US, the cost to society is estimated to be well over $100,000 per measles case! This includes not just the cost of treating the sick patient but of protecting the public from further spread of disease. This doesn’t even include the cost to businesses for parents’ time off to attend to sick children and other private-sector expenses. Nor does it include the costs of raising and supporting individuals permanently injured by the disease. By immunizing the population and responding quickly to imported measles cases, further costs – and potentially deadly or debilitating illness – can be prevented. Laboratories are but one link in the chain of the public health response. Confidence in the performance of laboratory assays is a key component of that link.
At the same time, not all public health laboratories can be expected to perform all tests for measles – or any other disease for that matter. No laboratory has unlimited resources, and public health labs are faced with limitations coming from federal, state, and local budget constraints. So, in the public health laboratory community, we need to work together to support each other where needed. Of course, the US Centers for Diseases Control and Prevention (CDC) have historically provided the extra support and reference testing services that public health laboratories rely on. But with current fiscal cutbacks, laboratories cannot always count on that to be the case.
To discuss these issues is more depth, with a specific focus on measles testing included, APHL’s VPD project hosted a meeting of experts in March to discuss various national laboratory capacity models that may help confront the challenges of VPD testing. The meeting participants noted that currently many public health laboratories utilize a shared-services model for mutual support; but they also acknowledged the lack of sustainability of this type of model. Having a national laboratory capacity model where each public health laboratory can maintain the baseline testing capability that they desire, while having the ability to access additional non-CDC reference services for complex testing and surge capacity, was seen by the meeting participants to be an acceptable, if not urgently needed, solution. The existence of public health laboratory resource centers for this type of support for reference testing, additional PT programs, and subject matter expertise, are seen as universal needs for all types of VPD testing. This type of collaborative national effort to confront existing VPD testing challenges can help public health laboratories support each other and maintain a level of preparedness that will allow them to be ready to respond to many emerging public health threats, such as importation of measles.
The World Health Organization has targeted measles for worldwide elimination. For this disease to begin a comeback in the US due to a lack of relatively small investments would be an embarrassment and a national shame. Elimination of measles is not a goal of just some poor countries overseas where the disease is still endemic. We in the public health system in the US are all part of this effort as well, whether we realize it every day or not. Now is not the time to be complacent by cutting back funding for prevention and control efforts, because to do otherwise would risk catastrophic situations and massive inputs of resources. Of course, by resources, I mean money – money that state governments currently cannot afford to spend on preventable situations.
APHL and the VPD project are doing their part within their role to maintain vigilance against measles. I hope that my efforts in this project help make our roles be successful. Now, I don’t expect my grandmother from Arkansas, or the street vendors I encountered in Livingstone, Zambia, to understand all the work that I do calculating standard deviations for PT results, reviewing laboratory testing algorithms, or analyzing the factors of various laboratory capacity models for public health laboratory resource centers. But I hope they do understand the value that these efforts have on society as a whole, helping to keep us all healthy – and happily ignorant of this devastating disease.
As I said, I have never seen a case of measles. With the continued great efforts of all my colleagues in the public health field, I hope I never do.