NTP has gathered a significant database of results collected on various NTP animal toxicity studies. To evaluate study results and follow changes in the biology of our test species, we maintain a historical summary of the observations made on the untreated or control groups from individual studies. These data are divided into categories depending on the study type. Due to a variety of factors that can influence response, historical control data may be identified by: Species, sex, route of administration, vehicle, study type, or laboratory. These data for control animals are periodically updated.
Learn the history of rat models used by NTP
Commentary: Update on Animal Models for NTP Studies contains a thorough discussion on rat strain selection considerations. The following history summarizes part of the discussion.
For more than 30 years, NTP used the inbred F344/N rat for toxicity and carcinogenicity studies. Over time, this substrain developed decreased fecundity, sporadic seizures, and idiopathic chylothorax. The F344/N possessed other health issues inherent to the strain including high rates of mononuclear cell leukemia and testicular neoplasia.
In 2005, NTP held the NTP Workshop: Animal Models for the NTP Rodent Cancer Bioassay: Stocks and Strains – Should we Switch?. Workshop participants recommended three options to NTP:
- Establish another colony of the F344 rat from another source,
- use an F1 hybrid, or
- use an outbred stock of rat such as the Wistar Han or the Sprague Dawley.
NTP temporarily switched to the F344/NTac rat and then selected the Wistar Han rat [Crl:WI (Han)]. However, in several studies with perinatal exposure, the average litter sizes were smaller than expected, the litters had a high variability in sex distribution, and pregnancy rates in time mated Wistar Han rats were not acceptable.
Consequently, NTP adopted the Hsd:Sprague Dawley SD rat as the default NTP rat strain. NTP's decision came after much deliberation including consideration of historical data from eight previous NTP cancer studies using the female Sprague Dawley rat, and very favorable data on litter size, sex ratio, and body weight.
Chronic Toxicity and Carcinogenicity Studies
In the pathology tables, tumor incidence is defined as the number of animals exhibiting a tumor type divided by the number of animals examined and is expressed as both raw counts and percent. The data for control animals are compiled from the most recent five-year window.
- The pathology tables present the mean, standard deviation, and range of tumor incidence among studies, along with the number of studies summarized.
- The growth and survival curves present the mean for each route/species/sex group of control animals along with the 5th and 95th percentile.
- Note: The historical controls data for genetically modified models are displayed separately.
Developmental and Reproductive Toxicity Studies
The NTP Historical Control database for fetal defects from stand-alone prenatal development (i.e. teratology) studies or modified one generation studies (MOG) is provided here. Note that fetal findings (Column C) are broken up by exam type (Column A), followed by body area (Column B). Data are presented as the number of fetuses or litters with a finding and the percentage calculations are in parentheses.
- Rows in bold reflect the total number of fetuses or litters per finding. Columns labeled “TOTAL_FETUS” and “TOTAL_LITTER” indicate the total number of findings per fetus and per litter in all studies presented here.
- Columns labeled “MIN_FETUS”, “MIN_LITTER”, “MAX_FETUS”, and “MAX_LITTER” indicate the minimum and maximum number of fetuses or litters with that finding.
Table of Historical Controls
Note: Historical Controls prior to 2016 have been archived. These archived materials include routes and vehicles for growth and survival. Email us or use our contact form to request a list or copy of Historical Control archived materials.
How to search with filtering and sorting
Search for particular tables by filtering or sorting the table. As you begin to type your search entry, the page will filter the table results by text. For example, type "F344" to see Fischer F344/N Rats rows.
To sort the table by a specific column, click the up/down filter arrow in the table header for that column. When clicked, the column headers will sort the table by ascending or descending order. If only one arrow is displayed, that column is sorted in the direction of the arrow. To sort more than one column, click the first column header, and then hold the shift key and click on additional column headers.