Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5866091/
Citation: Buckingham, E. M., Foley, M. A., Grose, C., Syed, N. A., Smith, M. E., Margolis, T. P., Thurtell, M. J., & Kardon, R. (2018). Identification of Herpes Zoster-Associated Temporal Arteritis Among Cases of Giant Cell Arteritis. American journal of ophthalmology, 187, 51–60. https://doi.org/10.1016/j.ajo.2017.12.017
Title: “Identification of Herpes Zoster-Associated Temporal Arteritis Among Cases of Giant Cell Arteritis”
The article begins with an explanation of the pathophysiology of giant cell arteritis. It explains that GBA is a vasculitis of the superficial temporal arteries due to an underlying inflammatory process against an unknown antigen/s. Additionally, all of the nerves involved (the ones that innervate the temporal arteries) are nerves that can contain latent varicella-zoster virus. Since these nerves (trigeminal ganglion) is the most common site of herpes zoster (shingles), resulting in herpes zoster opthalmicus, it’s been question whether GCA is caused by herpes zoster antigen deposition in the temporal artery. A recent study that assessed this topic actually found herpes zoster antigen in 74% of temporal artery biopsies obtained from patients with previously diagnosed GCA. Because of that, this study was done to retest for the presence of herpes zoster antigen in temporal artery biopsies of GCA patients from other institutions.
The study used a retrospective search of databases at the University of Iowa and Washington University for temporal artery biopsies from 2014 to 2017. A total of 25 patients with GCA confirmed histopathology on their temporal artery biopsies were included. Another 25 patients with symptoms of GCA but negative temporal artery biopsies were used as controls. The temporal artery biopsies from patients with confirmed GCA were evaluated using immunohistochemistry assays to test for herpes zoster antigen. Of the 25 patients in the confirmed GCA group 3 tested positive with herpes zoster-specific IHC assay. In comparison, the 25 patients with temporal artery biopsies negative for GCA were also tested for herpes zoster antigen with the IHC assay, and all patients were negative. Of the 3 patients with positive herpes zoster antigen and biopsy-proven GCA, one case was especially significant because the patient had herpes zoster ophthalmicus diagnosed 3 weeks before the onset of their GCA symptoms.
With that being said, the study observed many false-positive results from the zoster-specific IHC assays, particularly in the presence of temporal artery calcifications. The article attributed this to the attachment of antibodies to the calcifications themselves. However, the 3 patients with confirmed GCA who tested positive for herpes zoster antigen were reexamined to assure that the calcifications did not account for the VZV-positive IHC results, and they were not. Overall, there was no significant association between GCA-positive histopathology and herpes zoster antigen positivity in the majority of temporal artery biopsies from GCA patients. Therefore, the study concludes that it is not recommended to treat all patients with GCA with antivirals, unless there is an immediate past history of herpes zoster. There were many limitations to the study. First of all, the study produced many false-positive results and unclear results which all had to be disregarded. Second, the study only used 25 patients with confirmed GCA and 25 patients with negative histopathology results for GCA. This comes out to a total of 50 participants, which is a small sample size. Additionally, the 3 patients out of 25 who had true-positive results for herpes zoster antigens were not significant enough to impact the overall results of the study; however, if the sample size was larger and a greater number of patients from other institutions were used this number could’ve been greater (or smaller, thereby creating a better depiction of the results). Additionally, the study used a retrospective cohort study, which is less reliable than other studies including meta-analyses, systematic reviews, and randomized controlled studies, all of which produce higher level evidence for future use.
