20 research outputs found
Establishing new positive ranges for anti-phospholipid antibody tests based on the local population
Introduction:
According to past and current guidelines from the International Society on Thrombosis and Hemostasis on the laboratory criteria for antiphospholipid antibody syndrome (APS), antiphospholipid antibody (anti-cardiolipin (aCL) and anti-beta2-glycoprotein 1 (aB2GP1)) concentrations are an integral component of the diagnostic criteria for APS. However, external quality control exercises have highlighted high variability between commercially available aCL and aB2GP1 assays. Due to lack of both international standards and common human monoclonal antibodies, guidelines recommend that test results be considered positive if greater than the 99th percentile of a particular population. The objective of this study was to determine the 99th percentile of a New Mexico reference population and compare those against cutoffs recommended by one manufacturer of aCL and aB2GP1 assays.
Methods:
Whole blood samples in sodium citrate were collected from 120 healthy donors and stored at -70 degrees C for up to 12 months prior to testing. Concentrations of aCL and aB2GP1 were determined using the BioPlex 2200 System (Bio-Rad Laboratories, Hercules, CA). Results were combined with those from 37 samples previously used to verify manufacturer proposed cutoffs of greater than or equal to 20 units for all assays. The results were ranked and the 99th percentile determined. Newly derived cutoffs were applied to 1,118 aCL and 1,140 aB2GP1 results retrieved from our laboratoryâs data warehouse over a 12-month period.
Results:
See Table. Based on our populationâs 99th percentile cut-off values, 27 previously negative individuals would now be labeled positive, whereas only 3 previously positive individuals would now be labeled as negative; the majority of patient results did not change.
Table. 99th percentile determinations from validation and verification studies, and number of positive results using manufacturerâs cut-off (â„20 units) versus 99th percentile cut-offs. (see attachment).
Conclusions:
Given guideline recommendations that a local population be used to establish cut-off values, we have changed our cut-off values to the 99th percentile of our population. Interestingly, these cut-offs were similar to those established by Bio-Rad Laboratories during their validation. It is unclear why a uniform value of greater than or equal to 20 units was applied as the FDA-cleared cut-off
Recommended from our members
Hemostasis testing and therapeutic plasma exchange: Results of a practice survey
IntroductionPerforming therapeutic plasma exchange (TPE) with albumin replacement decreases coagulation factor and platelet levels. No defined guidelines exist regarding laboratory testing to assess hemostasis in patients undergoing TPE.Materials and methodsA survey to evaluate hemostasis testing with TPE was distributed using online survey software. One response per institution was analyzed based on a hierarchical algorithm, excluding membrane filtration users, resulting in a maximum of 120 respondents per question. Descriptive analysis was performed with results reported as the number and/or frequency (%) of respondents to each question.ResultsThe practices represented vary by institution type, number of apheresis procedures per year, and performance of TPE on children. Prior to TPE planned with albumin replacement, many respondents obtain laboratory studies for almost all patients (54.9% outpatients and 68.7% inpatients); however, some do not routinely obtain laboratory studies (9.7% outpatients and 4.4% inpatients). Hemoglobin/hematocrit, platelet count, fibrinogen, partial thromboplastin time (aPTT), and international normalized ratio (INR) are obtained prior to all TPE by 62.5%, 53.4%, 31.0%, 18.1%, and 17.7% of respondents, respectively; however, 1.0%, 8.7%, 29.0%, 38.3%, and 35.4%, respectively, do not routinely obtain these studies. Variation was observed in laboratory threshold values for action; the most common reported were hemoglobin/hematocrit reference range and >1.5 times reference range (tied, 28.1%), and INR >1.5 (20.7%).ConclusionsPractice variation exists in hemostasis laboratory testing and threshold values for action with TPE. Further studies are needed to determine optimal hemostasis testing strategies with TPE.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147803/1/jca21666.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/147803/2/jca21666_am.pd
Guidance on the Critical Shortage of Sodium Citrate Coagulation Tubes for Hemostasis Testing
Recent manufacturing problems and increased utilization has created a shortage of 3.2% sodium citrate blood collection tubes used for coagulation testing, causing stakeholders such as hospitals, clinics and laboratories, to find suitable alternatives. Considerations for in-house citrate blood collection tube preparations or purchasing commercial products from unknown manufacturing sources is of a particular concern to laboratories that perform coagulation testing. It is well recognized that variability exists between citrate blood collection tube manufacturers, thereby making any transition to new blood collection methods more challenging than simply switching to a new source. This document provide provisional guidance for validating alternative sources of sodium citrate blood collection tubes (commercial or in-house preparations) prior to clinical implementation