NOVELTY - A device configured for receiving a sample, comprises a moiety indicative for the presence of an analyte in the sample, where moiety comprises a magnetic and/or magnetizable label (1) having a diameter greater than 100 nm; and the device further comprises an amount of a salt (51) for dissolving in the sample to reduce aggregation of the moiety when in contact with the sample.    USE - As device configured for receiving a sample such as blood, blood plasma and blood serum (claimed). The assay is used in testing congestive heart failure (CHF), myocardial infarction or heart failure or hyperparathyroidism/hypoparathyroidism using moiety indicative for the presence of troponine I and/or T, NT-proBNP or PTH.    ADVANTAGE - The addition of salts to the sample prevents or at least reduces the aggregation of the magnetic and/or magnetizable labels of the moieties that are present for binding to the binding surface. Hence, a more accurate and precise signal relative to the concentration is detected per binding event leading to the improved reproducibility and reliability of the assay method. The combination of KCl and KBr is particularly effective to reduce cluster formations in samples in which cardiac troponin I, NT- proBNP or parathyroid hormone PHT as the analyte of interest. The device may have a magnetic field generator for attracting the magnetic or magnetizable labels to the binding surface. This reduces the time required for the binding reaction at the binding surface by virtue of the increase of the moiety concentration at the binding surface.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method of determining the presence of an analyte in a sample, involving providing moiety with a binding surface for binding the moiety, contacting the sample with the moiety, and measuring the presence of moiety on the binding surface to determine the presence of the analyte, and dissolving an amount of a salt in sample for reducing aggregation of the moiety in the sample before or at least during measuring.    DESCRIPTION OF DRAWING(S) - The figure shows schematic view of an apparatus.    Magnetizable label (1)    Sample chamber (2)    Salt (51)    Sample inlet (52)    Filter (53)