method for determining the level of neutralizing anti-drug antibodies (swims) in a biological sample from a subject treated with a biological drug, a prognostic method for assessing a subject's responsiveness to treatment with a biological drug, to monitor disease progression and the early prognosis of disease recurrence, device for detecting anything in a biological sample of a subject treated with said biological drug, kit, method for determining the level of an active biological drug in a biological sample of a subject treated with said disease biological drug