QUESTION: We have adopted using your viral panel. Could you explain how you interpret a positive IgG in any of the following: Chlamydia pneumoniae, Mycoplasma pneumoniae, Parvo, HHV 6, EBV. My understanding is that IgM being positive is current infection (and for EBV the early antigen). What if IgG is positive? Do you ever test CMV? Or any other viruses?

ANSWER: Typically we run ASO, C and M pneumo, Lyme, EBV, Candida and H pylori on the “average” sick patient as these are most high yield tests. Parvo definitely in Joint Pain pts. The rest we order if casting a wide net for the truly chronically ill to see what their exposure load is. IgM is only positive for a short time in acute infection, so if you test outside that window (of 4-7 through 20-30 days after acute response) the patient will be acute and IgM negative. Good thing is that if you see an IgM elevation you have a real acute to Tx.

I have a bunch of disparate papers on IgG’s and long term infection – none “sewn up” other than in my brain… I like this one from the point of view that possibly persistent high IgG titers may indicate higher immune activity and inflammation etc.

Blum A, Peleg A, Weinberg M. Anti-cytomegalovirus (CMV) IgG antibody titer in patients with risk factors to atherosclerosis. Clin Exp Med. 2003 Nov;3(3):157-60. PMID:14648230

Abstract: Studies have demonstrated cytomegalovirus (CMV) DNA particles in restenotic lesions in atherosclerotic coronary arteries. We have shown that high (>1:800) anti-CMV IgG antibody titers in the serum are associated with active coronary disease and with post coronary angioplasty restenosis. In this study we assessed the anti-CMV antibody titer in patients with risk factors for atherosclerosis (but without documented clinical manifestations). One hundred and eighly-seven patients (men and women aged 40-80 years) that were admitted to the Department of Internal Medicine were recruited to this prospective study. All had at least one risk factor for atherosclerosis, and none had documented coronary artery disease. Fasting blood samples were drawn on admission. Risk factors included hypertension, diabetes mellitus, active smoking, hyperlipidemia, and a positive family history. Ninety-three age- and sex-matched individuals without atherosclerosis risk factors served as the control group. One Hundred and twentysix patients had high anti-CMV antibody titers (>/=1:800) compared with none in the control group. Although 80 patients (90%) in the control group were seropositive, none had anti-CMV IgG antibody titers higher than 1:400. The statistical difference between the patients and the control group was highly significant ( p<0.0001). An immunological response against CMV (expressed as an anti-CMV IgG antibody titer) could be a marker of a long-standing immunological reaction causing an inflammatory response that eventually would cause advanced clinical atherosclerosis. We suggest that anti-CMV antibody titer should be used as an early predictor of atherosclerosis. Our findings support the infectious theory and an association between CMV infection and atherosclerosis at an early stage, maybe even years before clinical events occur.

I also have some which pretty clearly show that following serial IgG can lead to dx of recurrence if the titer increases from “baseline”. It is not exact but in the bigger picture helpful I believe. So while on screening with the CFS type patient a bunch of IgG pos only may tell past ‘load’ if they have flare sx and an increase in IgG for a viri or bact it may indeed indicate flare of infection without IgM.

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