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Date of last update: 10/12/2017.

Forum Name: Other infections

Question: ELISA - neg, Western Blot - pos: meaning?

 CocoLyme - Thu Aug 12, 2010 2:22 pm

For the past 5 years, I've had parkinsonian symptoms, which they've been calling Parkinson's although more than one neurologist has said that I don't present like typical Parkinson's. I also have various other symptoms: migratory joint pain, vision problems, recurrent/resistant/or opportunistic infections.

In March, I had the Lyme ELISA done. It came back negative - 0.28. Because of the various ongoing problems, my doctor ordered a Lyme Western Blot, with all bands reported. It came back positive:
IgM - 18, 30, 31, 34, 41, 83-93 (23-25 indeterminate)

IgG - 18, 23-25, 41, 58, 66 (34, 39 indeterminate)

What does this mean?
 Dr.M.Aroon kamath - Sun Aug 29, 2010 12:57 pm

User avatar Hi,
The ELISA test for Lyme disease tests for the presence of IgM isotype antibodies against B. burgdorferi (Bb). As it has high false-positive rates, it is typically followed up with a second test using a technique called Western blotting. It is reported as a single number that refers to the relative quantity of antibodies.
It is still used as a screening assay as it has specificity rates of 90-100%. The test is fully automated.

IgM isotype class antibody (IgM WB) is the first to appear following the infection , followed by a predominantly IgG antibody synthesis after a period of weeks. Moreover, after B.burgdorferi exposure, early (even inadequate) treatment can render an affected individual permanently seronegative. Therefore, in early or treated patients, seropositivity may not indicate 'active' Lyme disease. After successful teatment, if a patient is monitored serologically, IgM would show a rise for about a month, followed by a slow decline. However, it may remain positive in a considerable number of individuals for greater than one year. Therefore a persistent lower levels of IgM do not always imply persistent infection.
(Lyme disease - United States, 1993. MMWR Morb Mortal Wkly Rep 1994;43:564-71).

Unfortunately, the sensitivity of the ELISA varies considerably (ranging from 55% to 90%) depending upon the clinical manifestations and duration of infection. A single number is reported that reveals the relative quantity of antibodies in the patient’s serum against the agent of Lyme disease.

The western blot test detects and measures the levels of the IgG isotype class antibody. Since the antibody response develops slowly, during the early stage of the disease the test may have a sensitivity of only 50-75%, meaning that the test only detects the disease in 50 to 75 percent of those who truly have it.
(American Family Physician; Diagnosis of Lyme disease; Depietropaolo, Powers et al.; 2005).

However,in later stages of the disease, false negative results are uncommon and so,the test sensitivity in late stages of the disease averages over 95 percent. ELISA/Western blot can also return false positives.

Criteria vary for the interpretation of Western blot in the United States and in Europe. Earlier, the interpretation needed visual inspection of the intensity of certain "bands" by expert technicians. Presently, automated machines are able to perform this and thus, minimizing the chances of "subjective error". Within the US, the Centers for Disease Control advocate a standard method for evaluating the Western blot as positive: 2 out of 3 bands (23, 39 or 41 kD) on the IgM or 5 out of 10 bands on the IgG (18, 23, 28, 30, 39, 41, 45, 58, 66, 93). One drawback of this method (despite its advantage of providing uniformity) is that, the listed “specific” bands do not include certain other bands known to be specific for Bb (ex.,31 kD and 34 kD).

Thus, diagnosing Lyme disease based solely on the interpretation of the test values poses many problems. It has therefore been recommended that the diagnosis should take into consideration the "pretest probability". The more closely the patient's symptomatology matches and the more endemic the disease is in an area, the higher the pretest probability of the disease becomes.

It appears that you are concerned that your "Parkinson-like" tremors could be as a result of Lyme disease.

For early neurologic disease (facial and other cranial nerve palsies, and radiculoneuropathy), a CSF/serum ratio value of 0.5 for IgM and IgA in paired serum and CSF antibody testing, is considered significant.

For suspected late Neurologic (CNS and Peripheral) type of Lyme disease, serology is an essential. These patients usually have positive serologic tests, unless they had been previously treated or immunosuppressed. It is extremely unlikely to have CNS Lyme disease in the context of negative serologic results. A positive finding in paired serum and CSF antibody testing generally diagnoses CNS Lyme disease. By antibody capture ELISA, a positive result is defined as a ratio of CSF to serum IgG antibody levels of 1.5 or higher.

PCR testing on CSF is available but not highly sensitive in this setting and seems to have a lower sensitivity than antibody levels or ratios. In the setting of negative serology and negative CSF antibodies, it is highly unlikely to see a positive PCR in CSF. A positive PCR result does not indicate definitively that current infection is present, but it only strongly suggests current or very recent infection.

Parkinson-like tremors can occur in another condition known as 'Essential Tremor Syndrome' (ET). You can get more information on this topic by clicking on the following URL.
Best wishes!

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