Letter to the Editor

Properly Describing Individually Ventilated Caging Systems in Scientific Manuscripts

Dear Editor,

The first individually ventilated caging system (IVC) was developed in 1979 by Edwin Les and initially marketed commercially in 1980. A number of companies have subsequently developed IVCs with varying types of airflow mechanics over the ensuing 37 years. However, the scientific literature continues to use “Individually Ventilated Caging” as an all-encompassing term despite marked differences among the varying systems and rarely is the system described in sufficient detail in manuscripts in which they are evaluated. An uninformed reader may incorrectly assume that an article using one type of IVC can be applied to all IVC systems or may not be able to fully understand the system evaluated. A PubMed search conducted on June 15, 2017, using the search term “individually ventilated cages,” yielded 76 articles published between 1995 and April 2017. One of the articles was a “product profile”. Of the remaining 75 publications, none of the manuscripts provided details about the type of IVC used in the title of the study, including the 4 most recently published in JAALAS^1,2,4,5and only 1 manuscript provided this information in the abstract. Furthermore, several manuscripts did not provide the details of the type of IVC used in the study anywhere in the manuscript. In the materials and methods (M and M) section, only 38 of 64 manuscripts provided any operating details of the system. The remaining 11 articles were either abstracts (N= 4) or the publications were not available online (N = 7). However, the parameters provided to describe the system varied greatly and were not consistent among manuscripts. Many of the articles provide valuable information on the benefits and/or risks of using a specific IVC system; therefore, conclusions must be restricted to the system studied and should not be extrapolated to others.

Although an IVC classification system was proposed in 1999, neither this nor any other system has been adapted. ² The proposed terminology would at least provide the reader with a general understanding of a system’s operational principles without viewing the manuscript’s M and M section.

To address these concerns, we propose that the following parameters be included in a manuscript’s M and M section when reporting on IVCs in scientific journals such as JAALAS:

• Airflow mechanics

  1. Method by which air is supplied to the cage as well as the location of the supply air orifice/diffuser in the cage

  2. Method by which air is exhausted from the cage as well the location of the exhaust air orifice, if the cage is provided a single point of exhaust, or a description of the capture/canopy system, if present

• Rack ventilation

  1. Presence or absence of supply and/or exhaust blowers

  2. Indicate and describe rack ventilation if a room or facility HVAC system is employed in lieu of a supply and/or exhaust blower

  3. A description as to whether and how the rack’s ventilation system is connected to a central ventilation system

  4. Filtration methods, if employed, including type and location(s)

• Air change rates

  1. The intracage air change rate expressed as the number of air changes per hour (ACH), and

  2. Description as to how this rate was determined

• Cage design

  • Description to include filters (size and type), if provided

  • Location of the feed container, baffles (if present), and the water bottle (size and type) or automatic watering lixit

• 5.Intracage air flow dynamics

  1. Intracage air velocities and locations of measurement (if known and how determined)

  2. Airflow distribution pattern (if known and how determined)

  3. Intracage air pressure differential with respect to ambient (magnitude and direction)

• Other parameters to include if assessing microenvironmental conditions

  1. Macroenvironmental temperature and humidity
     1. Method and frequency of measurement
     2. Measurement device calibration technique (if applicable)
  2. Type and volume of bedding used and if/how it was processed (e.g., irradiated or autoclaved)
  3. Stock/strain and number of animals per cage
  4. Biomass (weight) of animals per cage and how equilibrated between cages and/or groups

The inclusion of these important system characteristics will allow reviewers and readers to fully evaluate the system and methods employed and potentially allow for comparisons of different system types between studies.

Scott E. Perkins

Neil S. Lipman

Biographies

Responses to Drs Perkins’ and Lipman’s Letter to the Editor:

Dear Editor,

Considering that our article was specifically referenced in Dr Perkins’ and Lipman’s letter, we would like to respectfully respond to their concerns.

It is certainly true that differences exist among the various individually-ventilated caging (IVC) systems used in our industry, and some of these differences impact the interpretation of results of investigations. In these cases, the inclusion of type of IVC in the title and abstract may be appropriate if not desirable. However, if the thrust of an article is independent of the type of IVC system used, then it is our contention that its identification in the title and abstract is not useful if not distracting.

Our article, entitled “Ammonia levels and urine-spot characteristics as cage-change indicators for high-density individually ventilated mouse cages”,¹ is intended to provide a useful reference for those considering moving from a calendar-based cage change schedule to one based on urine spot characteristics, regardless of IVC system. The advantage to this approach is that it can be applied with many types of IVC systems. Thus, identifying the specific IVC system used in this study in the title and abstract would potentially limit the usefulness of this approach within our scientific community and distract from the main focus of the work.

In the Materials and Methods section of our article, we did indeed describe cage size and design, intracage air change rates, and micro- and macro-environmental parameters in sufficient detail to inform readers of the conditions present during this study.

We respectfully contend that the level of detail in IVC parameters proposed in Dr Perkins’ and Lipman’s letter be reserved for articles in which comparisons between IVC systems are specifically relevant and would affect the interpretation of results. That level of detail would have detracted from the main thrust of our article.

Respectfully,

Ida Washington, DVM, PhD, DACLAM – Director and Attending Veterinarian, Office of Laboratory Animal Resources, West Virginia University, Morgantown, WV.

Mark Payton, PhD – Professor and Head, Department of Statistics, Oklahoma State University, Stillwater, OK

Dear Editor,

We agree that standardization of nomenclature and description of ventilated systems is needed. Currently ventilated systems go by a variety of names including IVC (individually ventilated caging), ventilated rack system, and a variety of combinations of these words. Standardizing the naming of these systems would help ensure consistency when performing literature searches. In addition, these systems have extremely different mechanical and ventilation designs depending on the manufacturer and the model. To ensure reproducibility of data, we recommend that both the manufacturer and model number be listed in the materials and methods section. Adjustable settings such as negative or positive to the room and airflow rate setting should also be provided. Standardizing nomenclature and the information published in studies utilizing these systems would help to ensure consistency and reproducibility.

Sincerely,

Beth Bauer, Cynthia Besch-Williford, Marcus Crim, Robert Livingston, and Matthew Myles

Letters to the editor

Letters discuss material published in JAALAS in the previous 3 issues. They can be submitted through email (journals@aalas.org) or by regular mail (9190 Crestwyn Hills Dr, Memphis, TN 38125). Letters are not necessarily acknowledged upon receipt nor are the authors necessarily consulted before publication. Whether published in full or part, letters are subject to editing for clarity and space. The authors of the cited article will generally be given an opportunity to respond in the same issue in which the letter is published.