Biochemical markers of ongoing joint damage in rheumatoid arthritis - current and future applications, limitations and opportunities

Table 4 Parameters for optimal use and interpretation of markers

Biological parameters	Sampling parameters	Analyte features	Assay format	Assay parameters	Study parameters
Food intake [183]	Sample acquisition	Active enzyme	Competitive assay	Dilution recovery	Mode of action
Diurnal variation [184–188]	Sample matrix (serum, urine, plasma or synovial fluid)	Latent enzyme	Sandwich assay	Buffer robustness	Duration of study
Seasonal variation	Anticoagulant (EDTA, heparin, citrate)	Total protein	Monoclonal or polyclonal antibody	Range of quantization	Onset of action
Joint activity [189, 190]	Freeze-thaw cycles	Fragment of the protein [9]	Multiplex or other technique	Sensitivity and limit of detection	Number of samples, sampling frequency (time course)
Medical condition	Shipping and storage conditions		Sample volume	Specificity and selectivity of pathology and parameter	Patient population^a

Compilation of parameters known to influence biological variation or analytic performance of a given biochemical marker. These parameters include, but are not limited to, biological variation or analytical performance of a given biochemical marker. ^aAge, gender, menopause status, ethnicity, duration of rheumatoid arthritis, prior treatments such as TNF antagonists, concomitant medications such as corticosteroids, estrogen, SERMs, and bispohosphonates, and comorbidities such as osteoporosis, diabetes, and hypertension with or without renal insufficiency.

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