Isocitrate as calcium ion activity buffer in coagulation assays.

Area of Science:

• Biochemistry
• Hematology
• Clinical Diagnostics

Background:

• Physiological calcium (Ca2+) activity is crucial for blood coagulation.
• The role of Ca2+ buffering in diagnostic coagulation assays requires investigation.
• Searching for compounds to buffer Ca2+ at ~1.3 mmol/L without interfering with coagulation.

Purpose of the Study:

• To identify compounds that buffer Ca2+ activity at physiological concentrations (~1.3 mmol/L).
• To assess if Ca2+ buffering improves diagnostic efficacy in global coagulation tests.
• To modify the activated partial thromboplastin time (APTT) assay using a suitable Ca2+ buffer.

Main Methods:

• Evaluated 11 candidate compounds for Ca2+ buffering capacity and coagulation interference.
• Selected isocitrate as the optimal Ca2+ buffer due to its properties.
• Modified the APTT assay with isocitrate to achieve buffered Ca2+ activity (~1.3 mmol/L) and analyzed patient samples.

Main Results:

• Identified citrate and isocitrate as suitable Ca2+ buffers; isocitrate was preferred.
• Isocitrate-modified APTT maintained Ca2+ activity at 1.60 ± 0.07 mmol/L, lower than the original APTT (2.73 ± 0.20 mmol/L).
• The modified APTT demonstrated greater patient deviation from normality (4.3 ± 5.7 vs. 3.6 ± 5.0), indicating improved diagnostic efficacy.

Conclusions:

• Isocitrate effectively buffers Ca2+ activity at physiological levels and acts as an anticoagulant.
• The modified APTT assay using isocitrate shows enhanced diagnostic efficacy.
• Isocitrate represents a promising agent for improving Ca2+ buffering in coagulation diagnostics.