[Which sample for the transport of mycoplasma, eSwab® or dry swab?] / Quel prélèvement pour le transport des mycoplasmes, eSwab® ou écouvillon sec ?

Mycoplasma hominis (MH) and Ureaplasma urealyticum (UU), belonging to mycoplasmas, are implicated in genital and urinary infections. These bacteria are extremely sensitive to environmental factors but remain detectable by culture methods. This study aimed to compare performance of detection on samples performed on eSwab® or dry swabs. Eighty-five genital samples were prospectively collected on dry- and e-Swab, at the Dynabio Croix-Rousse laboratory (Lyon, France), from January to March 2017, searching for mycoplasma infection. After incubation for 48 hours, cultures were qualitatively and quantitatively analyzed by a single qualified operator. On these samples, 23 specimens sampled on dry swabs were positive for UU and 2 for MH (versus 26 and 4 for eSwab). Quantification on eSwab® and dry swabs were statistically correlated (r=0.9118; and r=0.7155; p< 0.01 respectively) without discrepant results. No sample was double-positive during this study. With an important sensitivity (without alteration of the bacterial quantification) and regarding to the gravity of this infection on at-risk patients, as young and/or pregnant woman, the eSwab® sampling seem to improve the pre-analytic phase. However, the benefice to use these sampling methods for long-term conservations has to be evaluated.

How to handle adsorption of cerebrospinal fluid amyloid ß (1-42) in laboratory practice? Identifying problematic handlings and resolving the issue by use of the Aß42/Aß40 ratio.

INTRODUCTION: We aimed to investigate factors defining amyloid ß (1-42) (Aß1-42) adsorption during preanalytical workup of cerebrospinal fluid (CSF). METHODS: CSF was transferred to new tubes ≤4 times. Variables tested were different polypropylene tube brands, volumes, CSF Aß1-42 concentrations, incubation times, pipettes, vortex intensities, and other CSF proteins, including hyperphosphorylated tau and Interleukin 1 Receptor Accessory Protein (IL-1RAcP). An enquiry assessed the number of transfers in current practice. RESULTS: In diagnostic practice, the number of transfers varied between 1 and 3. Every tube transfer resulted in 5% loss of Aß1-42 concentration, even 10% in small volumes. Adsorption was observed after 30 seconds and after contact with the pipette tip. Tube brand, vortexing, or continuous tube movement did not influence adsorption. Adsorption for Aß1-40 was similar, resulting in stable Aß1-42/Aß1-40 ratios over multiple tube transfers. DISCUSSION: We confirmed that adsorption of CSF Aß1-42 during preanalytical processing is an important confounder. However, use of the Aß1-42/Aß1-40 ratio overcomes this effect and can therefore contribute to increased diagnostic accuracy.