[Do not use the "not reported" option]

EXAMPLE:

Histopathology (Poor - females): Significant concerns were raised regarding the procedural methods for histological evaluations. Specifically, no information was provided on the number of slides evaluated, how slides were selected for evaluation, and how lesions were judged. The sampling of 10 animals/ group is typical for subchronic studies, although larger sample sizes are typically preferred. (Poor/Critically deficient - males): In addition to the issues above, significant concerns were raised regarding the usability/interpretation of the data for males. "In the 13-wk exposure study, almost all the exposed male mice died after the first day of exposure".

Biochemical and urinalysis measures (Poor - females): Significant concerns were raised regarding the procedural methods for biochemical and urinalysis measurements. Specifically, no information was provided on the diagnostic kits or whether serum, plasma or whole blood were used. The sampling of 10 animals/ group is typical for subchronic studies, although larger sample sizes are typically preferred. (Poor/Critically deficient - males): In addition to the issues above, significant concerns were raised regarding the usability/interpretation of the data for males. "In the 13-wk exposure study, almost all the exposed male mice died after the first day of exposure".

Organ weights (Adequate - females): Procedural methods for organ weight measures were not described in detail, but since methodology is fairly straight-forward and qualitative results were provided for relative and absolute weights, the organ weight procedures were considered 'adequate'. The sampling of 10 animals/ group is typical for many subchronic studies, although larger sample sizes are typically preferred. Note: relative organ weights are often preferred for the liver and other organ weights as changes in absolute weights are considered less indicative of a histological effect, particularly when there is evidence of changes in body weight [Bailey SA, Zidell RH, Perry RW. 2004. Relationship between organ weight and body/brain weight in the rat: What is the best analytical endpoint? Toxicol Pathol. 32(4):448-66. PMID: 15204968]. However, for kidney, absolute weights were more predictive of kidney histopathology compared to relative weight, even in animals that suffered exposure-related body weight loss. [Craig EA, Yan Z, Zhao QJ. 2015. The relationship between chemical-induced kidney weight increases and kidney histopathology in rats. J Appl Toxicol. 35:729-36. PMID: 25092041]. Significant concerns were raised regarding the usability of the data for males. (Poor - males): Significant usability/interpretation concerns were raised for males "In the 13-wk exposure study, almost all the exposed male mice died after the first day of exposure".

RATING GUIDANCE: In good studies, there are no notable concerns about aspects of the procedures for, or the timing of, the endpoint evaluations.

Based on the endpoint evaluation protocol used for the endpoints of interest, specific considerations will typically include:

Concerns regarding the sensitivity of the specific protocols for evaluating the endpoint of interest (i.e. assays can differ dramatically in terms of their ability to detect effects), and/or their timing (i.e. the age of animals or time of day at assessment can be critical to the appropriateness and sensitivity of the evaluation). This includes both overestimates or underestimates of the true effect, as well as a much higher (or lower) probability for detecting the effect(s) being assessed.
Concerns regarding the specificity and validity of the protocols. This includes the use of appropriate protocol controls to rule out non-specific effects, which can often be inferred from established guidelines or historical assay data. It may be considered useful for insensitive, complex, or novel protocols to include positive and/or negative controls. This also considers the utility of the specific procedural details (e.g., how lesions were characterized) for measuring effects.
Concerns regarding adequate sampling. This includes both the experimental unit (e.g., litter; animal) and endpoint (e.g., number of slides evaluated). This is typically inferred from historical knowledge of the assay or comparable assays.

Note: Human relevance of the endpoint is not addressed during study evaluation; for undersampling without blinding (e.g., sampling bias), this will typically lead to gross overestimates of effect; sample size is generally not a reason for exclusion.

NTP 2007

Study evaluation

Animal bioassay experiments