Applicability assessment of clinal samples for rapid detection of Y. pestis by up-conversion technology-based immunochromatographic assay

Objective To explore the suitable clinical samples for rapid detection of Y. pestis by up-conversion technology-based immunochromatographic assay ( UPT-ICA ) and establish a standardized sample processing method.Methods A total of 464 clinical samples including serum, sputum, pus, tracheal secretions and cerebrospinal fluid were collected, and after mixed with the sample diluent at a ratio of 1 : 9, they were used to evaluate the specificity of UPT-ICA. The national reference of Y. pestis and 141 clinical samples of various types were mixed to prepare simulated positive samples containing 105 CFU/mL of Y. pestis for evaluation of the detection sensitivity. By increasing the proportion of sample diluent and digestive fluid, the sample processing method were explored. Based on the detection results, the methods for processing of clinical sample were improved. Furthermore, various types of samples were selected to evaluate the specificity and sensitivity of the UPT-ICA method for detecting Y. pestis on the basis of new processing methods.Results The sensitivity of UPT-ICA to Y. pestis of national reference was 105 CFU / mL, which was higher than that of colloidal gold immunochromatographic assay. The specificities of UPT-ICA for tracheal secretions and cerebrospinal fluid were 100%. The false positive rates of normal serum, hemolytic serum, and lipemic serum samples were 2.35%, 8.70%, and 12.64%, respectively, indicating that hemolytic and lipemic samples are not applicable. When diluted at a ratio of 1:99, the false positive rate for normal serum samples decreased into 0.58%. When sputum and the digestive fluid were mixed at a ratio of 1:1, one false positive result was generated, with a false positive rate of 1.20%, while no false positive result was observed at a ratio of 1:2. Three out of 42 pus samples were shown to false positive. When the concentrations of liver and spleen homogenates of mice were 10 mg/mL and 100 mg/mL respectively, the specificity was not affected. The sensitivity of UPT-ICA for simulated positive samples mixed with bacteria can all be maintained at 105 CFU/mL. Through improving processing method, the false positive rate of UPT-ICA for all clinical samples were reduced into 0.59% from 7.14%, with a invariant sensitivity.Conclusions The reagent for detection of Y. pestis based on UPT-ICA method can quickly and accurately detect all kinds of clinical samples after corresponding standardized treatment.