At the various conferences they attend throughout the year, members of the DNA Connexions team sometimes hear that the Lyme panel we offer is too sensitive. Recently, we even were told by a doctor that our test was detecting Lyme – at the incubational phase – in patients who were both non-symptomatic and regionally excluded (i.e., living in non-Lyme parts of the country). We take these concerns seriously, as they directly impact the health and subsequent treatment plans of those who seek our testing services.
Accordingly, in this article we would like to discuss several issues. To begin, we need to have a look at the general principles of scientific testing. After having done that, we will turn our gaze to the particular question of the DNA Connexions Lyme panel. After doing the latter, we will address the above-referenced questions of hypersensitivity and false-positivity, as well as our plans for the immediate future.
Scientific and Clinical Laboratory Testing in General
Sensitivity and specificity are common terms for assessing in quantitative terms the accuracy of a given testing method. In other words, they measure whether and how well that method is able to distinguish between disease and its absence. They are, thus, the two elements that measure the validity (i.e., accuracy) of a given test. Let’s look closely at them in order to see how they are related and, more importantly, how they are distinct.
Sensitivity “is the probability that a test will indicate ‘disease’ among those with a disease.”1 A given person is tested for Lyme disease.Being in fact infected with Lyme, his or her test results accurately indicate this diseased, or infected, state. Thus, sensitivity indicates “positive in disease.”
Specificity, meanwhile, refers to that same test’s ability to exclude those who are not diseased. In other words, specificity “is the fraction of those without disease who will have a negative test result.”1 What does this mean in practice? Taking the example given above, another person, who is not diseased, is tested for Lyme. The test results accurately exclude a Lyme diagnosis from that person.
These characteristics of sensitivity and specificity are inversely proportional to one another. The higher the sensitivity, the lower the specificity; the higher the specificity, the lower the sensitivity.2
Let’s attempt to sum up all of this succinctly. A tested subject is either diseased or non-diseased. A test result, meanwhile, is either positive or negative. And, both positives and negatives can be either true or false. A “true positive” is an accurate diagnosis of some disease. A “false positive” is an inaccurate diagnosis (i.e., a misdiagnosis) of a disease. A “true negative,” for its part, is an accurate conclusion of being non-diseased, while a “false negative” is an inaccurate conclusion of being non-diseased (i.e., where the tested individual is in fact infected.)
Finally, a highly sensitive test runs the risk of yielding some false positives, while a highly specific one is liable to yield a number of false negatives. While these distinctions may require some reflection, one thing is abundantly clear: both false positives and false negatives should be minimal in a good test. In other words, a good test is highly accurate. It diagnoses disease where it is present and excludes it where it is absent.
The DNA Connexions Lyme Panel
Now, let’s consider the DNA Connexions Lyme panel in particular. What makes it a uniquely efficient and highly valuable tool for detecting Lyme?
With regard to specificity, our panel is designed to be on the species-specific level. In this case, specificity particularly refers to the capacity of a testing method to discriminate or differentiate between molecular or cellular compounds that have similar characteristics. In other words, we do not just want to identify the genus of Borrelia. Rather, we want to determine which species of Borrelia we can accurately detect. The primers we use are continually checked against GenBank to ensure they are only amplifying the target species. This kind of testing modality in turn allows for the most direct methods of detection and subsequent treatment.
To apply statistical numeration to our test – when individuals ask what is the specificity of our test – the answer is as follows: In order to establish true specificity, there needs to be a gold standard testing method against which all other testing methods can be compared. Such a standard, however, does not yet exist for Lyme. If it did, then we would have individuals tested with both that gold standard and our own test, and we would compare the results to statistically evaluate our test’s strengths and eventual weaknesses. At present, this is not possible.3 We are, however, working toward establishing estimates of both sensitivity and specificity, but this requires a considerable amount of time and effort. Up to this point, both have been necessarily directed toward fulfilling test orders, due to our young company’s rapid expansion. We will update our website and associated literature as this information becomes available.
Nonetheless, we do have the medical questionnaire that patients often return with their intake paperwork. It is worth noting that our test results are very frequently in agreement with those of prior testing methods, as well as with these self-reported histories. We also have a number of practitioners who commonly report that our results are in agreement with their own diagnoses and previous testing results. On that note, it is important to reiterate that Lyme is a multi-regional and multi-symptomatic disease. In fact, it can be relatively asymptomatic, even masked by a plethora of seemingly unrelated symptoms. And, today it can be contracted anywhere.
Sensitivity, meanwhile, refers to the capacity of a given testing method to detect the compounds for which it has been designed. For example, we have been able to effectively kill Borrelia in our dilution studies with heat. We can, moreover, detect as few as ten organisms in a sample. So, yes, our test is fairly sensitive!
Admittedly, sensitivity is something of a two-edged sword. Yet, it is generally better to have too much of it rather than too little. After all, we live in an increasingly toxic world, and there is a lot of toxicity to be detected!
Finally, we must clearly distinguish between detection and diagnosis. Our test is graded as either positive or negative for Borrelia burgdorferi and other tick-borne disease co-infectors. If the DNA is present, then we can detect it. We are, however, limited to what is present in the sample provided for testing. This detection is not a diagnosis of Lyme disease. Some people are infected by B. Burgdorferi and/or certain co-infectors without ever knowing that they are so infected. Sometimes, a body’s strong immunological response is sufficient to clear the infection. ArminLabs in Germany, for instance, can measure the strength of such a response. We’ll speak more about this lab towards the end of this article.
On the other hand, some people are infected, and they are physically wiped out. We can detect B. burgdorferi in their submitted sample, and after that, we leave the business of making a formal diagnosis to appropriate medical professionals. We molecularly detect; they medically diagnose. This is a critical distinction to keep in mind.
Should anyone really be upset at being accurately diagnosed with an infectious disease different than the one for which he or she has been tested? For example, Lyme disease and mercury toxicity share twenty-one identical symptoms. Only highly accurate lab testing can distinguish between the two.
A Promising Step Forward
Frankly, we are confused by someone arguing that our test is either too sensitive or even too specific. After all, when it comes to disease, ignorance is definitely not bliss, especially when there are so many promising detection and treatment methods available today.
That having been said, this month we are now offering the Elispot test of Armin Labs, in conjunction with our existing Lyme assay. The Elispot can detect a single B. burgdorferi T-cell, and its sensitivity and specificity are estimated at 84% and 94%, respectively. The end result of this union will be a new, two-tiered testing modality, incorporating both direct and indirect methods. Thus, pathogenic presence and immunological response can be assayed together, making for even greater overall accuracy. Moreover, we intend this to be a constructive step toward establishing that much needed gold standard for Lyme detection and diagnosis.
Schwarzbach A. My Experience of Diagnosing and Treating Chronic Lyme Disease. In Focus: Lyme Disease. October 2017.
“The gold standard is the best single test (or a combination of tests) that is considered the current preferred method of diagnosing a particular disease (X). All other methods of diagnosing X, including any new test, need to be compared against this ‘gold standard’. The gold standard is different for different diseases. The gold standard for X may be considered outdated or inadequate, but any new test designed to replace the gold standard has to be, initially, validated against the gold standard. If the new test is indeed better, there are ways to prove that; following which the new test may become the gold standard.”
Please read the full article HERE.