Comparison of a commercial enzyme-linked immunosorbent assay with immunofluorescence and complement fixation tests for detection of Coxiella burnetii (Q fever) immunoglobulin M.

A commercially available enzyme-linked immunosorbent assay (ELISA) for the diagnosis of Q fever (PanBio Coxiella burnetii immunoglobulin M [IgM] ELISA, QFM-200) was compared to the indirect fluorescent antibody test (IFAT) for C. burnetii IgM and the complement fixation test (CFT). The ELISA demonstrated 92% agreement with the reference method (IFAT), and gave a sensitivity of 99% (69 of 70 samples) and a specificity of 88% (106 of 121). Specificity can be increased with confirmation by IFAT. CFT was found to have a specificity of 90% (107 of 119), although it was lacking in sensitivity (73%; 51 of 70). No cross-reactivity was observed in the ELISA with serum samples from patients with mycoplasma (n = 6), chlamydia (n = 5), or legionella (n = 4) infections, although 2 of 5 patients with leptospirosis and 1 of 4 samples containing rheumatoid factor (RF) demonstrated positive results in the ELISA. Results indicate that the performance of the PanBio C. burnetii (Q fever) IgM ELISA (F = 187) is superior to that of CFT (F = 163), and consequently the ELISA should be a useful aid in the diagnosis of acute Q fever.

Leptospirosis presenting as a haemorrhagic fever in a traveller from Africa.

Leptospirosis is usually a mild illness, although the severity of clinical manifestations may vary between the serovars of leptospires. In May 1993, a 48-year-old man from Ghana presented with severe icteric leptospirosis, initially managed as viral haemorrhagic fever. The causative serovar, bataviae, had not been previously diagnosed in human infection in Australia.

Detection of antibodies to Bartonella henselae in clinically diagnosed cat scratch disease.

OBJECTIVE: To determine the usefulness of an indirect immunoflourescence antibody test for antibodies to Bartonella henselae in diagnosing cat scratch disease (CSD). DESIGN AND SETTING: Retrospective case survey of 354 patients whose sera were tested for antibodies to B. henselae at Royal Perth Hospital, Perth, and the Institute of Clinical Pathology and Medical Research, Sydney. In 1994; and measurement of the background prevalence of antibodies to B. henselae. MAIN OUTCOME MEASURES: Prevalence of antibodies to B. henselae, odds of a positive titre (> or = 64) in patients with and without specific risk factors for CSD and clinical features of the disease; prevalence of antibodies to B. henselae in randomly selected blood donors. RESULTS: Demographic, clinical and cat contact data were available for 303 patients. Sixty-four (21.1%) had a positive titre, as did 53 of 98 (54%) patients with a history of cat contact and lymphadenopathy. This proportion increased to 62% (38 of 61 patients) in patients with a history of cat scratch or bite and to 90.3% (28 of 31) in those with cat contact, lymphadenopathy and histological evidence of granulomatous lymphadenitis. Patients who developed lymphadenopathy after cat contact were significantly more likely to have a positive titre than those without this history (odds ratio [OR], 20.8; 95% confidence interval [95% Cl], 9.6-46; P < 0.0001). Inclusion of a history of a cat scratch or bite significantly raised the odds of being seropositive (OR, 13.7; 95% Cl, 6.8-28.1; P < 0.0001), and the presence of granulomas on lymph node biopsy further increased the odds (OR, 124.4; 95% Cl, 19.4-1073; P < 0.0001). The prevalence of antibodies to B. henselae in random blood donors in New South Wales was about 5% (five of 102 sera samples). CONCLUSIONS: The immunofluorescence antibody test for B. henselae can be expected to be positive in just over half the patients with clinically suspected CSD, and it has a positive predictive value of 83%. In a significant number of cases the diagnosis cannot be made on the basis of the results of immunofluorescence antibody testing alone and further investigations, including lymph node biopsy, may be required.

Comparison of cell culture, mouse inoculation, and PCR for detection of Toxoplasma gondii: effects of storage conditions on sensitivity.

The sensitivity of detection of a wild-type strain of Toxoplasma gondii by cell culture, mouse inoculation, and PCR was determined following sample storage under conditions to which clinical specimens may be subjected during transport to the testing laboratory. Sample storage at -20 degrees C significantly decreased the sensitivity of mouse inoculation. The sensitivity of cell culture decreased with sample storage at 4 and -20 degrees C. The sensitivity of PCR was reduced by storage at 4 degrees C for 48 h, freezing, and heating. These findings have implications for the selection of appropriate methods for the direct detection of T. gondii organisms in suboptimally transported clinical samples.