ABC Calc in its version 3.1 (2006) now provides feed-back of results by individual antibacterial agent and route of administration. To achieve this, a new procedure for inserting rows in the "Enter consumption data" folder was introduced. Even when they have previous experience with ABC Calc, users of this version are advised to carefully read the instructions before starting to enter data.

ABC Calc is made available free-of-charge as a Microsoft Excel® file which has been saved under two different formats (see download box). Both files contain the same information, but differ in their size. Because of its smaller size, start by downloading the file ABC Calc 3.1. If problems occur with this file (mainly because it is not compatible with an older version of Microsoft® Excel), you should use ABC Calc 3.1_b.

ABC Calc is a simple computer tool to measure antibiotic consumption in hospitals and hospital wards. It transforms aggregated data provided by hospital pharmacies (generally as a number of packages or vials) into meaningful antibiotic utilisation rates. It was developed for the ESCMID Study Group on Antibiotic Policies (ESGAP) at the National Center for Antimicrobials and Infection Control, Statens Serum Institut (Copenhagen, Denmark), as part of the Danish Integrated Antimicrobial Resistance Monitoring and Research Programme (DANMAP).

Increasing levels in bacterial antibiotic resistance have renewed interest in obtaining relevant antibiotic consumption data, especially from hospitals. Although a standard methodology for calculating drug consumption has been developed during the past 20 years by the World Health Organization (WHO) through its Collaborating Centre for Drug Statistics Methodology (Oslo, Norway), this methodology is still poorly understood by microbiologists, infectious disease specialists, and often pharmacists. As a consequence, single research groups have developed their own methods and own measurement units to calculate antibiotic consumption, which has created confusion. Because very few data on antibiotic consumption in hospitals are published in the literature and these data are reported using various measurement units, it is almost impossible for a hospital to benchmark its consumption with other hospitals that are similar in size, affiliation and patient case-mix.

As recommended by WHO, ABC Calc reports hospital antibiotic consumption as a number of Defined Daily Doses (DDD) per 100 bed-days. For a specific drug, the DDD corresponds to the assumed average daily dose for its main indication in adults. DDDs are assigned by the WHO Collaborating Centre for Drug Statistics Methodology (Oslo, Norway) and updated once a year. ABC Calc uses the latest update, i.e. the 2006 version of the "ATC (Anatomical Therapeutic Chemical) Index with DDDs". Although DDDs might not reflect daily doses used in practice in a specific setting, they should NOT be modified, in order to allow comparisons among hospitals or hospital wards.

At present, ABC Calc only deals with “Antibacterials for systemic use“ also known as group J01 of the ATC classification system, as well as antibacterials in the following ATC groups: A02BD (Combinations for eradication of Helicobacter pylori), A07AA (Intestinal antiinfectives, incl. for selective decontamination of the digestive tract), J04A (Drugs fro treatment of tuberculosis) and P01A (Agents against amoebiasis and other protozoal diseases). Antibacterials for topical use, which are found in other ATC groups, are excluded. Additionally, ABC Calc cannot deal with several antibiotic combinations, mainly because DDDs have not been defined for these combinations. Before a solution is found to this problem, we nevertheless encourage users to record information on special antibiotic combinations to help identify the ones that are used in hospitals.