METHODS FOR ASSESSING BIOSPECIMENT INTEGRITY

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Methods for quantifying biospecimen sample integrity using markers of oxidation (Fig. 1). Under conditions of incomplete blood plasma/serum (P/S) sample freezing (including storage at -20 °C), two different forms of oxidation occur spontaneously at protein sulfur atoms namely S-cysteinylation of free cysteine residues (in which the oxidative event is disulfide bond formation) and sulfoxidation of methionine. Most P/S proteins are susceptible to at least one of these forms of oxidation. The reference ranges observed for S-cysteinylated-albumin (SCA) and methionine-oxidized-apoA-I (MOAl) in freshly analyzed samples are low and nonexistent, respectively— even in samples from patients experiencing conditions associated with oxidative stress, e.g., heart attacks. Thus, as oxidized forms of albumin and apoA-I, SCA and MOAl are useful markers of biospecimen integrity. The oxidative chemistries of SCA and MOAl are operational in other proteins and polypeptides. Thus, for rare cases in which the use of SCA or MOAl may be contraindicated, custom designed surrogate peptide probes based on SCA and MOAl oxidation chemistry may be fortified into samples at collection to serve as exogenous markers of P/S sample integrity.