A method for determining in vitro a difference in alpha-4-integrin activity in an individual with a disease or disorder selected from the group consisting of multiple sclerosis and inflammatory bowel disease, comprising: a) measuring a soluble molecule in a first biological sample obtained from an individual's body fluid, selected from the group consisting of blood, serum and plasma, immediately before the administration of an alpha-4-integrin inhibitor； b) measure the soluble molecule in a second biological sample, wherein the second biological sample has been obtained from a body fluid of the individual selected from the group consisting of blood, serum and plasma, within thirty-one days after the administration of the alpha-4-integrin inhibitor； c) determine if there has been a decrease in the levels of the soluble molecule between the first and second biological samples, where the decrease is correlated with a decrease in the alpha-4-integrin activity in the individual, and determine from this form if there is a difference in alpha-4-integrin activity in the individual after administration of the alpha-4-integrin inhibitor compared to what was before administration of the alpha-4-integrin inhibitor, and d) determine if an adjustment in the treatment of the individual is required, where the non-decrease, or a statistically very low decrease (p>； 0.05) in the levels of the soluble molecule between the first and second biological samples indicates an ineffective response to the inhibitor of alpha-4-integrin which requires an adjustment in the treatment of the individual； and wherein the alpha-4-integrin inhibitor is an antibody and the soluble molecule is sVCAM.Un método para determinar in vitro una diferencia en la actividad alfa-4-integrina en un individuo con una enfermedad o un trastorno seleccionado entre el grupo que consiste en esclerosis múltiple y enfermedad inflamatoria del intestino, que comprende: a) medir una molécula soluble en una primera muestra b
