title: The reduced local lymph node assay: the impact of group size.
abstract: The local lymph node assay (LLNA) is a skin sensitization test that provides animal welfare benefits. To reduce animal usage further, a modified version (rLLNA) was proposed. Conducting the rLLNA as a screening test with a single high dose group and vehicle control differentiated accurately between skin sensitizers and non-sensitizers. This study examined whether a reduction in animal number/group is feasible. Historical data were utilized to examine the impact of conducting the rLLNA with two mice/group. To assess the effect on the stimulation index (SI) 41 datasets with individual animal data derived using five mice/group were analysed. SIs were calculated on all possible combinations of two control and two high dose group disintegrations per minute (dpm) values. For 25 of 33 sensitizer datasets, > 96% of possible dpm combinations resulted in a calculated SI > 3. The lowest percentages of positive SIs were observed with weak allergens when, in the standard LLNA, the mean SIs would have been nearer to the threshold value of 3. The results indicate that moderate, strong and extreme allergens are more likely than weak allergens to be identified as sensitizers when group sizes of two mice are used within the rLLNA. It is concluded that a rLLNA with two mice/group would display decreased sensitivity and is inappropriate for use in hazard identification.
authors: The Procter & Gamble Company, Cincinnati, OH 45253-8707, USA. ryan.ca@pg.com <ryan.ca@pg.com>
authors: Cindy A
authors: CA
authors: Ryan
authors: Joel G
authors: JG
authors: Chaney
authors: Petra S
authors: PS
authors: Kern
authors: Grace Y
authors: GY
authors: Patlewicz
authors: David A
authors: DA
authors: Basketter
authors: Catherine J
authors: CJ
authors: Betts
authors: Rebecca J
authors: RJ
authors: Dearman
authors: Ian
authors: I
authors: Kimber
authors: G Frank
authors: GF
authors: Gerberick
mesh_terms: D000485:Allergens / Q000633:toxicity*; D000818:Animals; D017449:Dermatitis, Allergic Contact / Q000209:etiology; D003877:Dermatitis, Contact / Q000209:etiology*; D004305:Dose-Response Relationship, Drug; D005240:Feasibility Studies; D005260:Female; D007509:Irritants / Q000633:toxicity*; D023441:Local Lymph Node Assay; D008198:Lymph Nodes / Q000187:drug effects* / Q000473:pathology; D051379:Mice; D008808:Mice, Inbred CBA; D015203:Reproducibility of Results; D012107:Research Design; D018570:Risk Assessment; D018401:Sample Size
chemical_list: D000485:Allergens; D007509:Irritants