Method and system for detection of microbial growth in a specimen container

A method for determining whether microbial growth is occurring within a specimen container comprising the steps of:

• incubating the specimen container comprising a sample medium and a growth medium;
• obtaining a series of measurement data points from the specimen container while the specimen container is incubated and storing the data points in a machine-readable memory, the series of measurement data points representing a growth curve of microbial growth within the specimen container from the sample medium;
• performing with a programmed computer, a process comprising in parallel analytical methods (a) and (b), namely:
• (a) performing an analysis of variation in successive data points in the series of measurement data points, and
• (b) performing an analysis of changes in the area under the growth curve between sets of data points in the series of measurement data points;
• defining an interval of time during which analytical method (b) is prevented from making a determination of a positive condition in the specimen container when a difference between a current test value and a previous test value is greater than an upper threshold or less than a lower threshold, wherein the upper threshold and the lower threshold are based on the analysis of variation in successive data points in analytical method (a);
• determining a positive condition of microbial growth within the container from the measurement data points based on at least one of analytical methods (a) and (b);
• and
• ending the incubation when at least one of analytical methods (a) and (b) determines that the positive condition is present in the specimen container, or the process reaches a maximum incubation time.