Methods for improving the recovery of troponin I and T in membranes, filters and vessels

A method for diagnosing heart muscle damage, comprising:

• performing an immunoassay to determine the amount of cardiac troponin I in a sample from a subject, by combining
• a) an antibody conjugate comprising a signal generating element and a first antibody that specifically binds to cardiac troponin I complexed with troponin C and troponin T and specifically binds to free cardiac troponin I;
• and
• b) said sample, thereby forming a reaction mixture comprising said antibody conjugate bound to said cardiac troponin I, if present, in said sample;
• applying said reaction mixture to a surface comprising a second antibody capable of specifically binding to cardiac troponin I;
• capturing said cardiac troponin I—antibody conjugate complex on said surface via said second antibody, whereby the captured complex produces a detectable signal;
• detecting said signal;
• relating said signal to the amount of troponin I present in the sample, wherein said immunoassay is configured to provide assay results that are within a factor of two for (i) cardiac troponin I, uncomplexed to either troponin T or troponin C;
• and (ii) an equivalent concentration of cardiac troponin I in a complex with troponin T and troponin C and;
• relating the amount of cardiac troponin I present in the sample to the occurrence or nonoccurrence of heart muscle damage.