Development and testing of a rapid diagnostic test for bubonic and pneumonic plague.
BACKGROUND
Plague is often fatal without prompt and appropriate treatment. It affects mainly poor and remote populations. Late diagnosis is one of the major causes of human death and spread of the disease, since it limits the effectiveness of control measures. We aimed to develop and assess a rapid diagnostic test (RDT) for plague.


METHODS
We developed a test that used monoclonal antibodies to the F1 antigen of Yersinia pestis. Sensitivity and specificity were assessed with a range of bacterial cultures and clinical samples, and compared with findings from available ELISA and bacteriological tests for plague. Samples from patients thought to have plague were tested with the RDT in the laboratory and by health workers in 26 pilot sites in Madagascar.


RESULTS
The RDT detected concentrations of F1 antigen as low as 0.5 ng/mL in up to 15 min, and had a shelf life of 21 days at 60 degrees C. Its sensitivity and specificity were both 100%. RDT detected 41.6% and 31% more positive clinical specimens than did bacteriological methods and ELISA, respectively. The agreement rate between tests done at remote centres and in the laboratory was 89.8%. With the combination of bacteriological methods and F1 ELISA as reference standard, the positive and negative predictive values of the RDT were 90.6% and 86.7%, respectively.


CONCLUSIONS
Our RDT is a specific, sensitive, and reliable test that can easily be done by health workers at the patient's bedside, for the rapid diagnosis of pneumonic and bubonic plague. This test will be of key importance for the control of plague in endemic countries.
Chanteau
Suzanne
S
Institut Pasteur de Madagascar, WHO Collaborating Centre for Plague, Antananarivo, Madagascar. schanteau@cermes.ne
Rahalison
Lila
L
Ralafiarisoa
Lalao
L
Foulon
Jeanine
J
Ratsitorahina
Mahery
M
Ratsifasoamanana
Lala
L
Carniel
Elisabeth
E
Nato
Farida
F
D000911:Antibodies, Monoclonal; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008270:Madagascar; D010930:Plague / Q000175:diagnosis* / Q000401:mortality; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D013183:Sputum / Q000382:microbiology; D013997:Time Factors; D015010:Yersinia pestis / Q000276:immunology*
D000911:Antibodies, Monoclonal; D011933:Reagent Kits, Diagnostic