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Any modification to a validated assay must be evaluated in terms of the impact on the assay's performance characteristics and whether the assay remains fit for the intended purpose. The comparison is referred to as a 'method comparison', 'method comparability', 'method change', or 'comparative validation'. This review presents recommendations and examples of studies found in the current literature as a means of assessing minor modifications. In addition, the authors discuss common statistical approaches used for these comparisons.Toute modification apportée à un essai validé doit être évaluée afin de mesurer l’impact de cette modification sur les paramètres de performances de l’essai et déterminer si l’aptitude à l’emploi qui lui a été assigné demeure valable suite à la modification en question. Cette comparaison est désignée sous les termes de « comparaison de méthodes d’essai », « comparabilité de méthodes », « changement de méthode d’essai » ou « validation comparative ». Les auteurs font part de leurs recommandations et donnent des exemples d’études émanant de la littérature récente concernant l’évaluation de modifications mineures. En outre, ils examinent les approches statistiques couramment utilisées pour ces comparaisons.Toda modificación que se introduzca en un ensayo validado debe ser objeto de evaluación para determinar la influencia del cambio en las características de funcionamiento del ensayo y saber si este sigue estando adaptado a su función. Para referirse a la comparación, los autores emplean expresiones como ‘comparación de métodos’, ‘comparabilidad de métodos’, ‘cambio de método’ o ‘validación comparativa’. Los autores presentan aquí recomendaciones y ejemplos de estudios extraídos de la bibliografía actual como medio de evaluar modificaciones de importancia menor. Además, los autores examinan las lógicas estadísticas comunes utilizadas para estas comparaciones.

Any modification to a validated assay must be evaluated in terms of the impact on the assay's performance characteristics and whether the assay remains fit for the intended purpose. The comparison is referred to as a 'method comparison', 'method comparability', 'method change', or 'comparative validation'. This review presents recommendations and examples of studies found in the current literature as a means of assessing minor modifications. In addition, the authors discuss common statistical approaches used for these comparisons.

Two llamas with pulmonary tumors were examined. Llama No. 1 had multiple nodules throughout the lung that consisted histologically of solid clusters of polygonal to spindle cells with rare glandular differentiation. Intravascular emboli were common. Similar neoplastic masses were present in the kidney, heart, and liver. Immunohistochemically, neoplastic cells were positive for broad-spectrum cytokeratins (CKs), high- molecular weight CKs, CKs 5/6, and vimentin. The diagnosis was pulmonary carcinoma. Llama No. 2 had pulmonary nodules without extrapulmonary involvement. Microscopically, neoplastic cells formed acini lined by simple epithelium and solid cords of squamous cells that sometimes surrounded acini. Neoplastic cells were strongly positive for broad-spectrum CKs and weakly positive for thyroid transcription factor-1. The diagnosis was adenosquamous carcinoma. Pulmonary tumors account for 23% of neoplasms in South American camelids in our laboratory, making this the second most common type of neoplasm after lymphosarcoma.

A 9-year-old, intact male llama with mild ataxia and generalized malaise of 1 month's duration was euthanized following clinical evaluation. Excessive liver copper concentrations were found in the llama and also in clinically normal herdmates. This case documents multiple animals with increased hepatic stores from standard diets and mineral supplements.