Diagnostic accuracy of the rapid polymyxin test for colistin resistance in Gram-negative bacteria: a systematic review and meta-analysis.

BACKGROUND

Polymyxins are considered last-resort agents for treating multidrug-resistant Gram-negative infections; however, resistance is increasing worldwide. Broth microdilution is the standard reference method for colistin susceptibility testing; however, its technical complexity and prolonged turnaround time have prompted the development of the rapid polymyxin test. The clinical performance of these rapid tests across different bacterial species remains unclear.

OBJECTIVES

To evaluate the diagnostic accuracy of the rapid polymyxin test for detecting polymyxin resistance in Gram-negative bacteria.

METHODS

Data sources: PubMed, Scopus, Web of Science, and Embase (inception to 31 August 2025).

STUDY ELIGIBILITY CRITERIA: Studies evaluating rapid polymyxin tests against broth microdilution.

PARTICIPANTS

Gram-negative bacterial isolates.

INDEX TEST: Rapid polymyxin-based assays.

REFERENCE STANDARD: Broth microdilution.

ASSESSMENT OF RISK OF BIAS: Quality Assessment of Diagnostic Accuracy Studies 2 tool.

METHODS OF DATA SYNTHESIS: Bivariate random-effects model for summary sensitivity and specificity; hierarchical summary receiver operating characteristic curves; subgroup analyses by organism type.

PROSPERO: CRD420251140151.

RESULTS

Thirty-seven studies were included. The summary sensitivity was 0.966 (95% CI, 0.92-0.98), and the specificity was 0.945 (95% CI, 0.92-0.96). The area under the curve was 0.979, indicating high diagnostic accuracy. Subgroup analyses revealed species-specific variations, particularly between Enterobacterales and nonfermenters. Substantial unexplained heterogeneity was present (I2 = 86.1%) for sensitivity. Among Enterobacterales, sensitivity and specificity were consistently high, with low very major error rates.

DISCUSSION: The rapid polymyxin test demonstrates high diagnostic accuracy, particularly for Enterobacterales, but substantial heterogeneity and limited data for nonfermenters warrant caution. Implementation should be accompanied by confirmatory testing, especially in settings with a high prevalence of nonfermenting Gram-negative bacilli.