Sex hormones
    Relatively robust to various sample collection or processing methods
    Use of serum or EDTA or heparin plasma is acceptable
    Collect an ample volume of sample, as the assays require up to 0.3-0.5 mL per hormone
    If possible, collect a fasting, morning sample, and in premenopausal women, standardize the collection time in the menstrual cycle
    Delayed processing up to 72 hours is acceptable
    Store samples in airtight vials at ≤−70°C
Ascorbic acid and carotenoids
    Relatively robust to various sample collection or processing methods
    Use of serum or heparin plasma is standard; EDTA plasma is acceptable
    Can be exposed to indoor light, but not sunlight
    Has some seasonal variation; therefore, if assessing changes over time, collect in the same month or control for month in the analysis
    Processing samples can be delayed up to 1 week, but samples should be chilled
    Store in airtight vials at ≤−70°C
    For storage over long periods, best to include an acid stabilizer (e.g., metaphosphoric acid) if measuring ascorbic acid
    Can assay after two or fewer freeze-thaw cycles
Markers of inflammation
    Relatively few cytokines evaluated to date
    Modestly robust to various sample collection or processing methods
    EDTA plasma is best sample type, although serum and heparin plasma are acceptable
    Delay in processing time should be minimized (<48 hours) and samples kept chilled; tumor necrosis factor-α and IFN-δ can only be measured in samples processed immediately
    Store in airtight vials at ≤−70°C
    May assay after up to six freeze-thaw cycles depending on the analyte
Proteomic assays
    Sensitive to various sample collection or processing conditions
    Serum not recommended as it can introduce clot-derived peptides; use of EDTA, heparin, or citrate plasma depends on application
    Best to process sample to make it platelet poor to reduce platelet-derived peptides; consider inclusion of protease inhibitor(s) to reduce ex vivo cleavage of proteins
    Minimize number of freeze-thaw cycles (<2)
    Currently recommended processing procedure
        Remove platelets by centrifuging twice or by centrifuging followed by a filtration step at room temperature
        Process immediately or within 1-2 hours, although longer delays may be acceptable depending on the application
        Store in airtight vials
        Store in liquid nitrogen or −80°C in high-quality freezer
        Track all preanalytic variables