Immuno-PCR for the early serological diagnosis of acute infectious diseases: the Q fever paradigm

Abstract

To reduce the delay in diagnosis of Q fever, we have adapted the ultrasensitive immuno-PCR method for the detection of Phase II IgM anti-Coxiella burnetii. We compared its performance to ELISA, IFA and PCR using 31 acute Q fever sera and 50 control sera. The best sensitivity was obtained by iPCR (27 out of 31) followed by PCR (18 out of 31), ELISA (12 out of 31) and IFA (10 out of 31). A specificity of 92% was found by iPCR (3 false positive out of 40), 92% for ELISA (3 false positive out of 40) whereas PCR and IFA exhibited a specificity of 100%. Among the 31 Q fever sera, we compared the four methods for the detection of the early sera sampled during the two first weeks after the onset of symptoms and found a sensitivity of 90% by iPCR, 55% for PCR, 35% for ELISA and 25% for IFA. The results presented in this study suggest that iPCR is a promising, sensitive and specific method that can be used for the early diagnosis of acute Q fever and more generally for acute infections where traditional methods lack sensitivity.

From Q Fever to Coxiella burnetii Infection: a Paradigm Change

“…Immuno-PCR is an interesting method, combining the amplification power of PCR with the specificity and versatility of ELISA, allowing an improvement in sensitivity. We tested this method on a collection of serum samples from Q fever patients (373). Immuno-PCR had significantly better sensitivity than ELISA and IFA (90% versus 35% and 25%, respectively) in sera collected during the first 2 weeks after the onset of symptoms (373).…”

“…We tested this method on a collection of serum samples from Q fever patients (373). Immuno-PCR had significantly better sensitivity than ELISA and IFA (90% versus 35% and 25%, respectively) in sera collected during the first 2 weeks after the onset of symptoms (373). Its specificity was evaluated at 92%.…”

Bayesian Validation of the Indirect Immunofluorescence Assay and Its Superiority to the Enzyme-Linked Immunosorbent Assay and the Complement Fixation Test for Detecting Antibodies against Coxiella burnetii in Goat Serum

“…The culturing of C. burnetii is slow and has been reported to be unsuccessful using samples from some individuals despite their being positive by PCR, serology, and microscopy, suggesting that culturing is an unreliable method for C. burnetii detection (18). PCR methods of detecting C. burnetii DNA are widely considered to be highly sensitive (19). However, the relatively short period of time during which ruminants shed C. burnetii in feces, milk, vaginal mucus, and urine (5,9) limits the suitability of PCR for the detection of C. burnetii infection.…”

Cell Extract-Containing Medium for Culture of Intracellular Fastidious Bacteria

“…We tested 10 serum samples from patients with Q fever and 10 serum samples from patients without Q fever as confirmed by an immunofluorescent antibody (IFA) assay, which is the standard method for Q fever diagnosis (18). All steps of the ELISA were performed as previously described (19), with the following modifications: (i) the amount of antigen added per well was 0.5 g, and (ii) the serum was diluted 1:100 in PBS-Tween 0.1% supplemented with 3% bovine serum albumin (BSA). The mean value of the 10 negative sera Ϯ 2 standard deviations (SD) was set as the basal optical density cutoff value, and the results were expressed as the normalized ratio (optical density at 405 nm/basal cutoff value).…”