Background: Results for lupus anticoagulant (LA) are currently expressed as ratio of patient-to-normal clotting times (LA-ratio). Yet, numerical results do vary according to the method used for testing, thus making difficult the between-method comparison of results. We hypothesized that the standardization model currently used for the INR for patients on oral-anticoagulants (OAT) would be of value also for LA standardization. Patients and Methods: To test this hypothesis we determined a sensitivity index valid for LA (called LASI) for six LA-detection methods against a common-standard using two sets of calibration-plasmas: (i) normal-plasmas spiked with IgG derived from patients strongly-positive for LA or (ii) plasmas from LA-positive patients. The LASI was then used to convert the LA-ratio into the standardized-LA-ratio (SLA-ratio) according to the equation: SLA-ratio=(LA-ratio)(LASI). Results: We demonstrate that (i) the model is feasible because calibration plots of log-transformed clotting times obtained for the LA-detection methods-vs.-the common-standard gave acceptable LASI values; (ii) the model is effective because between-method variability expressed as coefficient of variation, which was 42.8% with results expressed as LA-ratio, decreased to 7.8% with results expressed as SLA-ratio; (iii) the LASI value calculated with the LA-positive plasmas is more effective in minimizing between-method variability than the LASI value calculated with IgG-spiked plasmas. Conclusions: A model of LA calibration similar to the INR for patients on OAT is feasible by using plasmas from LA-positive patients instead of patients on OAT. Potential application of the model are:(i) to compare the relative responsiveness of different LA-detection methods,(ii) to minimize differences between their results and (iii) to quantify LA potency.

Standardization of Lupus Anticoagulant. Feasibility Study of a Calibration Model to Minimize Between-method Variability / A. Tripodi, V. Chantarangkul, M. Clerici, C. Palmucci, E. Bison, A. Banzato, E. Biguzzi, V. Pengo. - In: THROMBOSIS RESEARCH. - ISSN 0049-3848. - 127:6(2011), pp. 589-594.

Standardization of Lupus Anticoagulant. Feasibility Study of a Calibration Model to Minimize Between-method Variability

A. Tripodi;
2011

Abstract

Background: Results for lupus anticoagulant (LA) are currently expressed as ratio of patient-to-normal clotting times (LA-ratio). Yet, numerical results do vary according to the method used for testing, thus making difficult the between-method comparison of results. We hypothesized that the standardization model currently used for the INR for patients on oral-anticoagulants (OAT) would be of value also for LA standardization. Patients and Methods: To test this hypothesis we determined a sensitivity index valid for LA (called LASI) for six LA-detection methods against a common-standard using two sets of calibration-plasmas: (i) normal-plasmas spiked with IgG derived from patients strongly-positive for LA or (ii) plasmas from LA-positive patients. The LASI was then used to convert the LA-ratio into the standardized-LA-ratio (SLA-ratio) according to the equation: SLA-ratio=(LA-ratio)(LASI). Results: We demonstrate that (i) the model is feasible because calibration plots of log-transformed clotting times obtained for the LA-detection methods-vs.-the common-standard gave acceptable LASI values; (ii) the model is effective because between-method variability expressed as coefficient of variation, which was 42.8% with results expressed as LA-ratio, decreased to 7.8% with results expressed as SLA-ratio; (iii) the LASI value calculated with the LA-positive plasmas is more effective in minimizing between-method variability than the LASI value calculated with IgG-spiked plasmas. Conclusions: A model of LA calibration similar to the INR for patients on OAT is feasible by using plasmas from LA-positive patients instead of patients on OAT. Potential application of the model are:(i) to compare the relative responsiveness of different LA-detection methods,(ii) to minimize differences between their results and (iii) to quantify LA potency.
Antiphospholipid syndrome; IgG; INR
Settore BIO/12 - Biochimica Clinica e Biologia Molecolare Clinica
Settore MED/09 - Medicina Interna
Settore MED/15 - Malattie del Sangue
2011
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/169526
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