ABSTRACTDiagnosis of chronic Q fever is difficult. PCR and culture lack sensitivity; hence, diagnosis relies mainly on serologic tests using an immunofluorescence assay (IFA). Optimal phase I IgG cutoff titers are debated but are estimated to be between 1:800 and 1:1,600. In patients with proven, probable, or possible chronic Q fever, we studied phase I IgG antibody titers at the time of positive blood PCR, at diagnosis, and at peak levels during chronic Q fever. We evaluated 200 patients, of whom 93 (46.5%) had proven, 51 (25.5%) had probable, and 56 (28.0%) had possible chronic Q fever. Sixty-five percent of proven cases had positiveCoxiella burnetiiPCR results for blood, which was associated with high phase I IgG. Median phase I IgG titers at diagnosis and peak titers in patients with proven chronic Q fever were significantly higher than those for patients with probable and possible chronic Q fever. The positive predictive values for proven chronic Q fever, compared to possible chronic Q fever, at titers 1:1,024, 1:2,048, 1:4,096, and ≥1:8,192 were 62.2%, 66.7%, 76.5%, and ≥86.2%, respectively. However, sensitivity dropped to <60% when cutoff titers of ≥1:8,192 were used. Although our study demonstrated a strong association between high phase I IgG titers and proven chronic Q fever, increasing the current diagnostic phase I IgG cutoff to >1:1,024 is not recommended due to increased false-negative findings (sensitivity < 60%) and the high morbidity and mortality of untreated chronic Q fever. Our study emphasizes that serologic results are not diagnostic on their own but should always be interpreted in combination with clinical parameters.

ABSTRACT.Purpose: To investigate the prognosis and complications in patients with peripheral multifocal chorioretinitis (PMC). PMC is a posterior or panuveitis characterized by chronic bilateral vitritis and punched-out lesions in the peripheral retina which occurs commonly in elderly white women and is associated with sarcoidosis. Prognosis and complications are largely unknown. Methods: A structured literature search in PubMed, Embase and Cochrane was performed to identify relevant articles. Articles were screened, and the remaining articles were critically appraised based on relevance and validity. Results: The search yielded 267 articles. Eight relevant articles were retrieved. All studies reported on moderate visual impairment. Macular oedema occurred in 60% of the patients with PMC (range, 0-71%), glaucoma in 27% (range, 25-43%) and an epiretinal membrane in 21% (range, 0-28%). In total, 47% had proven or presumed sarcoidosis. Treatment usually comprised topical corticosteroids, periocular steroid injections and systemic corticosteroids regularly in combination with methotrexate. Conclusion: The prognosis of patients with PMC is characterized by a rather poor visual outcome and the relatively high prevalence of complications. PMC is strongly associated with sarcoidosis. Solid proof for the treatment efficacy of PMC is lacking.