Comparison between urine culture profile and morphology classification using fluorescence parameters of the Sysmex UF-1000i urine flow cytometer

Abstract

Aims: To determine the usefulness of the fluorescence parameters generated by Sysmex UF-1000i flow cytometer for the rapid diagnosis of urinary tract infection by bacilli or cocci.

Methods and results: Urine samples (n = 1924) were studied by culture and microbiology and subsequently by cytometry, using BACT-Morph software and considering forward-scattered light (FSC) and fluorescent light scatter fluorescence parameters. BACT-Morph software showed moderate diagnostic accuracy (78·4%) to detect rod-shaped bacteria, with sensitivity of 82·4% and specificity of 62·5%. Forward-scattered (B_FSC) values of the bacterial channel were significant higher for the Gram-positive cocci category (P < 0·001). A cut-off of B_FSC ≥24·2, expressed in arbitrary units (analytical channel, ch), provided higher sensitivity (90·0%) but lower specificity (38·9%), and the diagnostic accuracy for Gram-positive cocci classification reached 62·0%.

Conclusions: Utilization of BACT-Morph software and bacterial channel fluorescence parameters (B_FSC ≥24·2 ch) offered an approximate discrimination of bacilli and cocci but the specificity was low, especially for FSC.

Significance and impact of the study: Further research is needed to establish the usefulness of flow cytometry for aetiological diagnosis.