How to Use Klimisch Scoring System to Assess Data Reliability

Little Pro on 2018-09-20

Data quality is very important for chemical risk assessment and regulatory decision-making. Klimisch et al (1997) developed a scoring system to assess the reliability of data from toxicological and ecotoxicological studies. This rating system has been extended to physico-chemical studies and is now accepted by many regulatory authorities and organizations. In this article, we will show you how to use the Klimisch scoring system to evaluate data reliability.

Klimisch Scoring System

Data is assigned to one of the 4 scores below. Generally speaking, only Klimisch scores of 1 or 2 can be used to cover an endpoint as reliable data. Klimisch score 3 and 4 data are only used as supporting studies or as part of a weight of evidence approach. ECHA's IUCLID 6 software has already included rationale for assigning Klimisch scores. It can also be found in the table below.

Score Description Assignment Criteria in IUCLID
1 Reliable without restriction
  • guideline study (preferably performed according to GLP)
  • comparable to guideline study
  • test procedure in accordance with national standard methods
  • test procedure in accordance with generally accepted scientific standards and described in detail
2 Reliable with restriction
  • guideline study without detailed documentation
  • guideline study with acceptable restrictions
  • comparable to guideline study with acceptable restrictions
  • test procedure in accordance with national standard methods with acceptable restrictions
  • study well documented, meets generally accepted scientific principles and acceptable for assessment
  • accepted calculation method
  • data from handbook or collection of data
3 Not reliable
  • significant methodological deficiencies
  • unsuitable system
4 Not assignable
  • abstract
  • secondary literature
  • documentation insufficient for assessment

Note: Results from QSAR are usually assigned to 2 or 4 in IUCLID. Expert judgement is needed.


Although well established and widely used, the Klimisch categories lack, however, detailed criteria for assigning data quality. A better tool to use is “ToxRTool” (Toxicological data Reliability Assessment Tool). It is an excel-based tool developed by ECVAM to provide comprehensive criteria and guidance for evaluations of the inherent quality of toxicological data.

ToxRTool consists of two parts, one to evaluate in vivo and one to evaluate in vitro data. It is applicable to various types of experimental data, endpoints and studies (study reports, peer-reviewed publications) and leads to the assignment to Klimisch categories 1, 2 or 3. One only needs to answer some questions about existing data and will get assigned Klimisch scores.

To download the tool, please click the link below.

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 Tags: Topics - CRAToxicology and Health Risk Assessment