Special pleading is the process of inventing a special reason to explain away inconvenient evidence or the lack of predicted evidence.
A popular web site about logical fallacies comments:
Humans are funny creatures and have a foolish aversion to being wrong. Rather than appreciate the benefits of being able to change one’s mind through better understanding, many will invent ways to cling to old beliefs. One of the most common ways that people do this is to post-rationalize a reason why what they thought to be true must remain to be true.
It’s usually very easy to find a reason to believe something that suits us, and it requires integrity and genuine honesty with oneself to examine one’s own beliefs and motivations without falling into the trap of justifying our existing ways of seeing ourselves and the world around us.
Special pleading in chronic Lyme groups
In online groups, patients are falsely told that they have Lyme disease based on single positive bands such as band 31, band 34, or band 41. The pseudoscience group ILADS seems to encourage confusion and misdiagnoses by asserting “a positive 31 or 34 band is highly indicative of Borrelia Burgdorferi exposure.”
This is a form of special pleading. Negative tests are ignored because they contradict the beliefs of the group. Most of the bands being negative even after months or years of symptoms is powerful evidence against a Borrelia Burgdoferi infection.
Since bands 31 and 34 almost always accompany other scored bands when a real Borrelia Burgdorferi infection is detected, one or two bands being detected usually indicates a spurious result.
Barbara Johnson, PhD, a scientist with the CDC who specializes in the Lyme disease and serological testing, wrote a very informative chapter in the book “Lyme disease: an evidence-based approach” in which she explains why bands 31 and 34 aren’t used in standardized testing.
The short explanation
Bands 31 and 34 aren’t that useful for predicting Lyme disease. In one study, bands 31 and 34 were only detected in about 15% of the Lyme samples and about 2% of the samples from healthy people.
Also notable is that the band 41 antibody reacted in 43% of the healthy people and 75% of the syphilis patients! That means a test result with a single band 41 is likely not indicative of a Lyme infection.
Dr. Johnson’s explanation
4.2.3 Why don’t the scoring criteria for immunoblots include OspA and OspB?
The bands at the 31 and 34 kDa positions of immunoblots are produced by OspA and OspB, respectively (Fig. 4.2). It has been recognized since the early 1990s that antibodies to OspA and OspB are infrequently detected and when they are observed, it is usually in patients with longstanding Lyme arthritis. Ma et al. (1992) wrote that ‘… antibodies against the 31- and 34-kDa proteins were rarely detected and, consequently, became less significant when compared with other protein bands in this study’. Steere’s laboratory reported in Dressler et al. (1993) that, although antibodies to OspA and OspB were detectable in some patients with Lyme arthritis or late neurological disease, the frequency of antibody responses to these polypeptides was not as high as to ten other antigens. Blot interpretation criteria that could best discriminate Lyme disease patients from controls therefore did not include scoring antibodies to OspA or OspB. When bands at 31 or 34 kDa are observed, they are virtually always in the context of a robust IgG response to a large number of scored antigens.
Patients may inquire specifically about why OspA is not scored when it was the basis for an effective vaccine. People naturally think of the usual way that vaccines work, neutralizing infection in a mammalian host, and expect a vaccine antigen to be a good diagnostic antigen. They may be unaware that the OspA vaccine works by killing B. burgdorferi in vector ticks as they feed. OspA is well expressed by B. burgdorferi in unfed ticks and is a suitable target for antibodies that enter a tick during a blood meal from an OspA-vaccinated host. When ticks are exposed to a blood meal and the body temperature of a mammal, B. burgdorferi stops expressing OspA. Another outer-surface protein, OspC, is expressed instead. Reciprocal expression of these two Osps has been demonstrated at the level of single cells. It is not surprising, therefore, that antibody responses to OspC are diagnostically useful in early Lyme disease, but responses to OspA are lacking.
In later manifestations of Lyme disease, especially Lyme arthritis, some people develop antibodies to OspA and/or OspB. OspA expression is upregulated in an inflammatory milieu such as an arthritic joint. OspA expression can be artificially upregulated in a controlled in vivo environment by exposure to zymosan, a yeast cell-wall extract that induces inflammation. Thus, it is no longer a paradox that B. burgdorferi expresses little or no OspA as it is transmitted to mammalian hosts, but that OspA can be produced late in the course of untreated Lyme disease.
Some claim that patients should be judged seropositive based on finding immunoblot bands solely at the 31 or 34 kDa positions, even when their serum is negative by an ELISA that uses whole-cell antigens. However, B. burgdorferi grown in culture expresses OspA and OspB abundantly and ELISAs made from cultured whole cells contain these antigens. Thus, samples from patients who have diagnostically significant levels of antibodies to OspA or OspB will react in a whole-cell-lysate ELISA. When an ELISA is negative but an immunoblot of the same sample is scored positive, it is probable that faint immunoblot bands are being ‘over-read’.
Fig. 4.2. Examples of conventional IgM (left panel) and IgG (right panel) immunoblots. Bands that are recommended for scoring* are labelled. Two additional bands in the IgG blot are also labelled (OspA and OspB at 31 and 34 kDa, respectively; see text). Blots are considered to be positive if two of the three indicated IgM bands or five of the ten indicated IgG bands (excluding OspA and OspB) are present at an intensity equal to or greater than the calibration control.
Left panel: IgM blot profiles for a patient with acute EM (lane 1) and for the same patient at convalescence (lane 2). Note the increase in the number and intensity of the bands at convalescence.
Right panel: IgG blot profiles for eight patients with later manifestations of Lyme borreliosis (lanes 1–8). P, Positive-control serum; N, negative-control serum; C, calibration control (weak positive control). The molecular mass is indicated (kDa). The calibration controls (weak positive controls) have been digitally enhanced for greater clarity in reproduction.
The scored IgG bands are 18 kDa, 24 kDa (OspC), 28 kDa, 30 kDa, 39 kDa (BmpA), 41 kDa flagellin (Fla), 45 kDa, 58 kDa (not GroEL), 66 kDa, and 93 kDa. The scored IgM bands are 24 kDa (OspC), 39 kDa (BmpA), and 41 kDa (Fla)
The figure above uses band 23 for OspC. According to the CDC, “Depending upon the assay, OspC could be indicated by a band of 21, 22, 23, 24 or 25 kDA.”