Requirements for the PODLOD calculator
This program should run in all modern browsers, e.g. Brave, Chrome, Edge, Firefox, Opera or Vivaldi.
For comfortable use, a PC or a notebook are recommended. PODLOD online can also be used on tablets, however, display of the tables may not be ideal and varies depending on the device and browser used.
The decimal separator may be a comma or a period. It might be converted depending on local settings and the browser.
To use PODLOD online, go to PODLOD.
Background information
For detailed information on PODLOD, the equations used and their derivation see:
C. Wilrich & P.-Th. Wilrich, Estimation of the POD Function and the LOD of a Qualitative Microbiological Measurement Method in: Journal of AOAC International (2009) 92(6), 1763-1772.
DOI: 10.1093/jaoac/92.6.1763, see also www.researchgate.net/publication/41485250.
This PODLOD program is referenced in ISO 16140-2.
Abbreviations
| PODLOD: | Probability of detection |
| LOD: | Limit of detection |
| CFU: | Colony forming unit |
| SD: | Standard deviation |
Revisions of the PODLOD calculator
PODLOD online, dated 2026-09-17, is the first online version of the PODLOD program (based on the PODLOD Excel-program, see Home).
Design of the experiment
In order to obtain reliable results, at least 3 informative inoculation levels d should be used. These preferably should correspond to a low, a target and a high inoculation level. A blank and a positive control can be used in addition but generally require only 1 tube each. Such a design is shown exemplarily in the table.
| Name of Matrix: | Example of typical design | ||
|---|---|---|---|
| Inoculation level | No. of tested tubes |
No. of positive tubes |
|
| CFU/A0 | CFU/g | ||
| d | n | y | |
| d = 0 = blank control | 1 | ||
| d = low inoculation level | 6 | ||
| d = target inoculation level | 6 | ||
| d = high inoculation level | 6 | ||
| d = positive control | 1 | ||
Equations used in the PODLOD calculator
Protocols applied in this calculator
| Case | Result |
|---|---|
| If a positive result was obtained the blank control (inoculation level d = 0), this is clearly an error and the test should be repeated after checking for possible causes, e.g. contaminated medium or faulty technique. | No calculation is carried out for that matrix and its data are excluded from the calculation of the combined results. |
| If no positive result was obtained for any of the inoculation levels, this suggests that the tubes were not inoculated, the medium does not support growth of the test organism or the primary sample did not contain the organism. The procedure should be checked carefully for possible errors. | The data of that matrix are included in the calculation of the combined results. |
| If only positive results were obtained for all inoculation levels (except for the blank control), this suggests that preparation of the inoculation levels was not done properly. The procedure should be checked carefully for possible errors. | The data of that matrix are included in the calculation of the combined results. |
| If a negative result was obtained for the positive control, this is clearly an error and the test should be repeated after checking for possible causes e.g. failure to inoculate the medium or wrong level of test organisms in the inoculum. | The data of that matrix are included in the calculation of the combined results. |