Table 1 Information on measured biomarkers in blood and synovial fluid samples incl. Sample treatment, storage and laboratory analyses

White blood cell count

Blood

EDTA

2–8 °C

Max. 24 h

Automated cell counting, ADVIA 2120 analyzer (Siemens Healthcare Diagnostics Inc., Deerfield, Illinois, USA)

[31, 78]

Synovial fluid

EDTA

2–8 °C

Max. 24 h

Counted in haemocytometer

[31, 78]

Total protein

Blood

Serum

1200 g for 10 min at 20 °C

2–8 °C

Max. 24 h

Biuret, ADVIA 1800 Chemistry System (Siemens Healthcare Diagnostics Inc., Deerfield, Illinois, USA)

[36]

Synovial fluid

EDTA

Max. 1 h at room temperature

Within 1 h

Refractometry

[31, 78]

Serum amyloid A

Blood

Serum

1200 g for 10 min at 20 °C

2–8 °C

Max. 24 h

Immunoturbidometry (LZ test SAA, EIKEN Chemical Co., Tokyo, Japan)

[79]

Synovial fluid

EDTA

Max. 24 h at 2–8 °C, then in aliquots at −80 °C

Within 7 months

[30]

Haptoglobin

Blood

Serum

1200 g for 10 min at 20 °C

Max. 4 h at room temperature then in aliquots at −80 °C

Within 7 months

Biochemical peroxidase assay in duplicates (Phase Range Hp Assay, Tridelta Development Ltd. Kildare, Ireland)

[60]

Synovial fluid

EDTA

Max. 24 h at 2–8 °C, then in aliquots at −80 °C

Within 7 months

Previously determined in porcine synovial fluid by ELISA [80]

Iron

Blood

Serum

1200 g for 10 min at 20 °C

2–8 °C

Max. 24 h

Colorimetric spectrophotometry (ADVIA 1650, Bayer A/S, Lyngby, Denmark).

[37, 78]

Synovial fluid

EDTA

Max. 24 h at 2–8 °C, then in aliquots at −80 °C

Within 7 months

Not previously reported in equine synovial fluid, but in synovial fluid of human patients by a colorimetric method using an automatic analyser (Aeroset, USA) [70]

Fibrinogen

Blood

Citrate

2–8 °C

Max. 24 h

Clauss method, automated coagulometric analyser (ACL 9000, Instrumentation Laboratory, Barcelona, Spain).

[22]

Synovial fluid

Citrate

1500 g for 15 min at 20 °C

Initially 15–30 min at room temperature then in aliquots at −80 °C

Within 17 months

QuickVet® Equine Fibrinogen™ Test (Scandinavian Micro Biodevices, Farum, Denmark)

Measured in synovial fluid in human osteoarthritis with automatic coagulometer (BFT II Dade Behring, Marburg, Germany) [17]

Thrombin-antithrombin

Blood

Citrate

1500 g for 15 min at 20 °C

Initially 15–30 min at room temperature then in aliquots

at −80 °C

Within 20 months

ELISA measured in duplicates (Enzygnost TAT micro test kit, Siemens Healthcare Diagnostics, Denmark)

[45, 81]

Synovial fluid

Citrate

Within 20 months

Not previously reported in equine synovial fluid, but with same assay in synovial fluid of human rheumatoid arthritis and osteoarthritis [14]

D-dimer

Blood

Citrate

1500 g for 15 min at 20 °C

Initially 15–30 min at room temperature then in aliquots at −80 °C

Within 21 months

Immunoturbidimetry in duplicates (STA-Liatest D-DI, Diagnostica Stago, Triolab, Denmark)

[82, 83]

Synovial fluid

Citrate

Within 18 months

[25, 26], both used a quantitative immune-turbidimetric latex agglutination assay (Miniquant, Biopool, Trinity Biotech, Wicklow, Ireland)