[Theoretic and practical contribution of bayesian inference to statistical process control: The experience of the Lyon Hospitals Board hemostasis laboratory]. / Intérêts théoriques et pratiques de l'inférence bayésienne dans la maîtrise statistique des procédés : retours d'expérience du laboratoire d'hémostase aux Hospices civils de Lyon.

Laboratories need to set up effective overall management of their internal quality control (IQC) and external quality assessment (EQA) results as key elements in statistical process control. Quality targets need to be defined, with methods to ensure durable control with respect to the relevant specifications. The hemostasis laboratory of the Lyon Hospitals Board (HCL, Lyon, France) uses model 3 from the Milan consensus conference, which is the state of the art in terms of quality targets, and uses a common EQA provider supplying as many real patient samples as possible. Giving priority to adopted methods, the lab optimizes the use of manufacturers' prior data: maximum acceptable inter assay coefficient of variation (CV) and prior IQC target values. Bayesian inference brings the method under control with respect to the manufacturers' prior data without the need for a preliminary phase. It links the IQC and EQA plans by the maximum acceptable CVs defined by the manufacturer.

Disk Diffusion Testing for Detection of Methicillin-Resistant Staphylococci: Does Moxalactam Improve upon Cefoxitin?

Disk diffusion testing is widely used to detect methicillin resistance in staphylococci, and cefoxitin is currently considered the best marker for mecA-mediated methicillin resistance. In low-inoculum diffusion testing (colony suspension at 106 CFU/ml), the addition of moxalactam in combination with cefoxitin has been reported to improve on cefoxitin alone for the detection of methicillin-heteroresistant staphylococci. However, moxalactam is absent from EUCAST and CLSI guidelines, which use high-inoculum diffusion testing (colony suspension at 108 CFU/ml), calling into question the potential interest of including moxalactam in their recommendations. The inhibition zone diameters of cefoxitin and moxalactam, alone and in combination, were evaluated for concordance with mecA and mecC positivity in a large collection of clinical Staphylococcus isolates (611 Staphylococcus aureus, Staphylococcus lugdunensis, and Staphylococcus saprophyticus isolates and 307 coagulase-negative staphylococci other than S. lugdunensis and S. saprophyticus isolates, of which 22% and 53% were mecA-positive, respectively) and in 25 mecC-positive S. aureus isolates using high-inoculum diffusion testing. Receiver operating characteristic, sensitivity, and specificity analyses indicated that the detection of mecA- and mecC-positive and negative isolates did not improve with moxalactam, either alone or in combination with cefoxitin, compared to cefoxitin alone. These findings were similar in both the S. aureus/S. lugdunensis/S. saprophyticus group and in the coagulase-negative staphylococci group. Our results do not support the use of moxalactam as an additional marker of methicillin resistance when testing with high-inoculum disk diffusion.