ObjectiveTo evaluate the diagnostic value of droplet digital PCR （ddPCR） for detecting Candida infections in critically ill patients.MethodsA ddPCR assay for Candida detection was established and optimized， including design of primers and probes， optimization of PCR reaction， and validation of analytical specificity and cutoff threshold. Clinical specimens were analyzed by ddPCR and fungal culture in parallel to assess clinical performance and reliability.ResultsThe ddPCR assay demonstrated high analytical specificity for Candida detection. The sensitivity and specificity of ddPCR for detecting Candida in clinical samples were 0.583 （95%CI： 0.433， 0.721） and 0.962 （95%CI： 0.924， 0. 982）. The ddPCR detection results were consistent with the fungal culture results （Kappa=0.604， P<0.05）. The total assay time for ddPCR was approximately 7 hours， substantially shorter than conventional fungal culture.ConclusionThe ddPCR assay provides reliable and rapid detection of Candida in critically ill patients with markedly reduced turnaround time compared with conventional culture. Given its high specificity and operational efficiency， the ddPCR-based method holds significant potential for clinical implementation as a complementary diagnostic tool.

Objective To establish a rapid detection method for invasive candidiasis based on droplet digital polymerase chain reaction(ddPCR).Methods We developed an assay system using a microtitre-based digital PCR platform and designed primer probes specific for four Candida species,namely Candida albicans,Candida smoothii,Candida near-smoothii,and Candida tropicalis.(1)The Limit of Blank(LOB)range and positive judg-ment value were determined by analyzing No Template Control(NTC)samples.(2)The Limit of Detection(LOD)range was determined by diluting positive samples with 10 replicate extractions at each concentration gradient.(3)The Linear Limit of Quantitation(LOQ)range was determined by repetitive testing of diluted samples.(4)The linear range limit was determined through gradient dilution of the positive samples.(5)The coefficient of variation(CV),calculated from the logarithmic values of the resultant concentrations,was assessed by extracting and test-ing positive samples in 12 repetitions at both high and low concentrations.(6)Method reliability was evaluated by calculating the CV from the logarithmic values of the resultant concentrations obtained from clinical samples with fungal culture results.Results The ddPCR assay detected Candida LOB at a range of 0～81 copies/mL,with a positive threshold set at≥3 positive microdroplets.The LOD and LOQ were determined to be 3×102 copies/mL.The linear range for detecting different concentration gradients was found to be between 3×102 and 3×107 copies/mL,with high correlation coefficients observed for Candida albicans(R2=0.999 5),Candida smoothii(R2=0.998 9),Candida near-smoothii(R2=0.999 4),and Candida tropicalis(R2=0.999).Additionally,the coefficient of variation for the resultant concentration logarithmic values was less than 5%,meeting precision requirements.Furthermore,preliminary validation using clinical specimens demonstrated consistent results compared to clinical culture findings.Conclusion ddPCR exhibits rapidity,high sensitivity,good repeatability,and high specificity in detecting inva-sive candidiasis in critically ill patients.This study highlights the potential value of droplet digital PCR as a diag-nostic tool for invasive candidiasis.