The availability of accurate and precise Fibrinogen concentration measurements throughout low, normal and elevated ranges are of significant utility in clinical practice. The assessment of elevated fibrinogen levels is valuable as a known marker of coronary heart disease, cerebrovascular disease, cancer, diabetes, hypertension, acute phase reactions, pregnancy, etc. Likewise, the decreased fibrinogen levels associated with liver disease, DIC, thrombolytic therapy, miscarriage, poor wound healing and intracranial hemorrhage support the premise that accurate quantification of very low levels of fibrinogen is needed. The Hemosil TM Fibrinogen-C XC Clauss Fibrinogen (FibC) assay measurement range for Instrumentation Laboratory (IL) ACL TOP family (ACL TOP/CTS) analyzers has been expanded to 30–1000 mg/dL. This assay has the capability of accurately measuring plasma fibrinogen in three mode segments: Near Normal for the 100–500mg/dL range, High Fib for samples 500 to 1000mg/dL and Low Fib for samples less than 100mg/dL. The accuracy of the expanded Fibrinogen assay was assured by calibration with the 2nd International Standard for Fibrinogen calibrator, plasma 98/612 and verification with the SCC/ISTH Secondary Coagulation Standard Lot # 3 as well as a 100 donor normal pool. Precision is consistent across the entire range. Normal, low and high samples demonstrated Total CVs of < 7%. The linearity of values across the expanded Fib C measurement range was established using a statistical evaluation based on CLSI EP6-A: Evaluation of the Linearity of Quantitative Measurement Procedures. Overlapping linearity of the 3 mode segments was demonstrated for Low Fib from 30–150 mg/dL, for Fib C from 85–500 mg/dL, for High Fib from 200 –1000 mg/dL as well as for the overall range of 30–1000 mg/dL. As noted, recovered values from Low Fib to Fib C and from Fib C to High Fib overlap when the tests are evaluated individually, but in practice, this Fib C assay will reflex seamlessly to the appropriate low or high test range. Deviation from Linearity, a statistical measure of goodness of fit, was low, less than 7% for 9 equidistant points between 30 and 1100 mg/dL. Linearity and accuracy were further confirmed in an extensive and statistically rigorous CLSI EP9 method comparison study of 200 samples representing a wide variety of clinical disorders Additional studies investigated interferences and other sample specific conditions. Measurements using reflexive modes to extend the Fibrinogen measurable range deliver timely, precise and accurate information to the practicing clinician over the wide diagnostic range of 30–1000 mg/dL.
Disclosure:Employment: Authors are employed at Instrumentation Laboratory, Lexington, MA, USA.