Microbiological Challenges in the Diagnosis of Chronic Q Fever

作者：Kampschreur Linda M^*; Oosterheert Jan Jelrik; Koop Annemarie M C; Wegdam Blans Marjolijn C A; Delsing Corine E; Bleeker Rovers Chantal P; De Jager Leclercq Monique G L; Groot Cornelis A R; Sprong Tom; Nabuurs Franssen Marrigje H; Renders Nicole H M; van Kasteren Marjo E; Soethoudt Yvonne; Blank Sybrandus N; Pronk Marjolijn J H; Groenwold Rolf H H; Hoepelman Andy I M; Wever Peter C

来源：Clinical and Vaccine Immunology, 2012, 19(5): 787-790.

DOI：10.1128/CVI.05724-11

Diagnosis 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 positive Coxiella burnetii PCR 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 %26gt;= 1:8,192 were 62.2%, 66.7%, 76.5%, and %26gt;= 86.2%, respectively. However, sensitivity dropped to %26lt;60% when cutoff titers of %26gt;= 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 %26gt;1:1,024 is not recommended due to increased false-negative findings (sensitivity %26lt;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.

• 出版日期2012-5