Testing for Lyme Disease is problematic for several reasons
'Scientifically, sensitivity (% of definite positive patients who test positive by the test in question) and specificity (% of well patients who test negative by the test in question) are measured against another test, such as CDC surveillance pos WB, which is how the patients are determined to be positive in the first place. As ALL tests for Borrelia lack sensitivity to some extent this makes the sensitivity and specificity of the test in question highly suspect, or limited. This, of course, means sensitivity and specificity are not really related to % of patients who ACTUALLY have the disease, but % who have been determined by a particular test of limited sensitivity to have the disease, a subset. As patients who have been definitely determined to have Borreliosis by the CDC criteria for surveillance, and the CDC are measuring the sensitivity of a new test against that, of course the sensitivity of that new test will be inflated, a great advantage if you are the holder of the patent of that new test. This would be especially so if the new test is measuring some parameter which is related in some way to the baseline test (such as both measuring antibodies to something).
In reality any of the various tests available if positive is a likely indication the patient has Borreliosis, but any one of them will have some false positives. The false positive rate is not scientifically possible to accurately determine from evidence. In Borreliosis the sceptics commonly cry "false positive" for any one test which shows positive, but they have no evidential basis on which to ground their claims. It is certainly helpful to the patient's cause to have 2 separate tests positive, making a false positive far less likely. In areas of medicine other than Lyme it is usually clinical suspicion plus one suggestive, not necessarily strong positive, test which would be taken as diagnostic evidence.
However, IF the judges (the CDC) are actively trying to protect the health insurance industry (which would appear to be the case, based on the evidence of their judgements), of course their current stance would make a lot of sense. If they applied the same level of criteria for all other infectious diseases, only a small fraction of patients with infections of all kinds would be diagnosable or treatable.'
I read the above explanation recently and have permission to share, it explains very clearly one aspect of the problems we have with Lyme serology.
Prof Perronne discusses other aspects of Serolgy in this publication
Calibration of serology
When Lyme serology was developed, no reliable method was available to be used as a gold standard for comparison. As most of the signs and symptoms are non-specific, no reliable clinical diagnostic score could be established. The low yield of culture and the difficulty involved in using the technique routinely were another major obstacle. A pragmatic cut-off level for the serologic tests had to be determined arbitrarily on blood donors (EUCALB, 1997; Assous, 2007). In the late seventies, when Lyme disease was first discovered, it was understandably thought to be a rare and regional phenomenon. Therefore, a low prevalence was set as experts were afraid the serologies would produce too many false positive diagnoses (EUCALB, 1997; Assous, 2007). Patients and control populations are ill-defined with a high variability in predictive positive and negative values from one test to another. Culture of B. burgdorferi or detection of its genome by polymerase chain reaction (PCR) may occasionally confirm the clinical diagnosis in seronegative patients, however none of these methods are sensitive enough to be considered reliable diagnostic methods, especially in routine practice (Schutzer et al., 1990; Nields and Kveton, 1991; Chmielewska-Badora et al.,2006; Brunner, 2006; Assous, 2007; Holl-Wieden et al., 2007; Aguero-Rosenfeld, 2008; Dietrich et al.,2008; Wallet et al., 2008). As a result, many patients suffering signs and symptoms compatible with Lyme disease, but whose test is negative, are falling by the wayside.
Possible causes of seronegativity
Several factors leading to seronegativity have been identified in confirmed cases of Lyme disease: (i) the arbitrary cut-off level of tests, (ii) the sequestration of antibodies in immune complexes, (iii) the wide variety of species and subspecies of Borrelia that co-exist in different parts of the world, and (iv) coinfections with other pathogens which may be responsible for some or all of the symptoms or which may alter the immune response (Schutzer et al., 1990; Brunner, 2006). The complex B. burgdorferi sensu lato includes (Table ): B. burgdorferi sensu stricto (including genetic diversity), B. afzelii, B. garinii (several serotypes) and additional species isolated in different parts of the world (Rudenko et al., 2009, 2011; Ogden et al., 2011). Some of these species have been isolated in symptomatic patients (Varela et al., 2004; Lopes de Carvalho et al., 2009; Rudenko et al., 2009; Stanek and Reiter, 2011; Branda and Rosenberg, 2013; Clark et al., 2013; Lee et al.,2014; Margos et al., 2014). B. spielmanii may cause early skin disease (Stanek and Reiter, 2011). B. bavariensis, B. bisettii, B. valaisiana, B. americana, B. andersonii, B. lonestari and more recently B. kurtenbachii have been isolated from patients with Lyme-like diseases (Varela et al., 2004; Rudenko et al.,2009; Rizzoli et al., 2011; Stanek and Reiter, 2011; Clark et al., 2013). The pathogenic role of B. lusitaniae, isolated in a case of vasculitis, remains to be substantiated (Rudenko et al., 2009). Despite such diversity in strains, most of the commercially available tests still rely on the original 1982 Massachusetts B31 isolate of B. burgdorferi. No diagnostic tool is available for routine detection of B. miyamotoi (Branda and Rosenberg,2013; Lee et al., 2014). Coinfections with other microbes add to the complexity of these illnesses (Table ). Among patients with early Lyme disease in the USA, 2–12% were found to also have human granulocytic anaplasmosis, and 2–40% babesiosis (Wormser et al., 2006). In Brazil, a Lyme-like syndrome, due to the tickAmblyomma, has been described and mobile non cultivable spirochetes could be visualized in patients' blood using a dark field microscope (Mantovani et al., 2007). A new tick-borne bacterial pathogen, CandidatusNeoehrlichia mikurensis, was reported in Switzerland (Fehr et al., 2010). An illustration of the limits of serology is the Scottish example: the sensitivity of the immunoblot was improved by using local Scottish strains of Borrelia (Mavin et al., 2007, 2009).
Conclusion and perspectives
The numerous complexities of Lyme disease make it an extremely difficult illness to fully comprehend. It remains a diagnostic challenge even for the best informed of clinicians. The lack of a gold standard for diagnosis renders the management of patients difficult and seriously hinders our ability to produce accurate statistics, especially as very similar syndromes could be due to other species of Borrelia. In some patients suffering from syndromes of unclear origin, following tick bite, other microbial agents could also be playing a role.
To read Prof Perronne full paper
Ying Zhang