S20 © American Society for Clinical Pathology AJCP / MEETING ABSTRACTS Am J Clin Pathol 2022;158:S1-S29 DOI: 10.1093/ajcp/aqac126 interference, we investigated the situation further. A pool of plasma was spiked with hydroxyurea. The spiked pool was serial diluted (x2, x4, x8, x16, x32, x64, x128) to ob- serve the creatinine results in the presence of and absence of hydroxyurea. The dilution series was analyzed using the Vista enzymatic creatinine and the Abbott i-STAT enzymatic creatinine methods. The i-STAT creatinine re- sults show increasing creatinine concentration from inter- ference as the concentration of hydroxyurea increased. The dilution series suggests increasing positive interfer- ence with hydroxyurea. Positive creatinine interference with hydroxyurea was not observed when analyzed on the Vista platform. Hydroxyurea is a widely used treat- ment for myeloproliferative disorders and also for man- aging sickle cell disease. Hydroxyurea is known to cause positive interference in the i-STAT enzymatic creatine method that uses electrochemical detection, with the de- gree of interference correlating with the concentration of hydroxyurea. The Vista colorimetric enzymatic creatinine method was not observed to have hydroxyurea interfer- ence. While both methods employ enzymatic reagent sys- tems the final detection approach is important. Patients undergoing hydroxyurea treatment should avoid i-STAT measurement systems for creatinine. A case report of type 2M Von Willebrand disease with unique mutations Xiaohua Qi, Yanan Fang; Albert Einstein College of Medicine, Department of Pathology Montefiore Medical Center, New York, NY Von Willebrand disease (vWD) is the most common in- herited bleeding disorder. It results from quantitative or qualitative defects of the von Willebrand factor (vWF) protein, and is divided into three types, namely type 1, type 2(2A, 2B, 2M, and 2N), and type 3 vWD. Here we report a case of 55-year-old female who presented with recurrent gastrointestinal bleeding due to angiodysplasia. Her past medical history is significant for vWD (type un- known) with hemoptysis, epistaxis and menorrhagia re- quiring Humate-P replacement multiple times. She has one sister with mild vWD of unknown type and 4 other siblings with no bleeding history. Coagulation testing shows normal PT and aPTT. Von Willebrand panel shows vWF antigen of 33%, VWF ristocetin cofactor ac- tivity of 15%, and Factor VIII of 87%. The ratio (VWF: RCo/VWF: Ag) is low (0.45) and the multimer pattern is normal. This is consistent with type 2M vWD. VWD gene sequencing shows heterozygous variants of c.4241T>G (p.Val1414Gly) and c.5227G>A (p.Val1743Met). Of note, one variant (c.4241T>G/p.Val1414Gly) has been re- ported in two individuals with type 2A but not in type 2M vWD. This may truly represent different types of vWD caused by same mutation or could be due to variation in testing and/or result interpretation among laboratories. The other variant c.5227G>A(p.Val1743Met) in A3 do- main has never been reported with uncertain significance. Further investigation including vWF panel testing and genetic analysis in family members would help charac- terize those mutations. Analysis of the Effects of High-Sensitivity Cardiac Troponin Confounding Factors on AMI Diagnosis Li Liu, Xueya Cai, Matthew Corsetti, Tanzy Love, Tai Kwong, Andrew Mathias; University of Rochester Medical Center High-sensitivity cardiac troponin (hs-cTn) plays an es- sential role in facilitating the diagnosis of acute myocar- dial infarction (AMI). However, there are several known confounding factors affecting hs-cTn concentrations, including sex, age and renal dysfunction. Women have significantly lower hs-cTn concentrations compared to men in presumably healthy populations and in patients presenting to the emergency department (ED). Increasing age leads to elevated troponin levels; and decreasing esti- mated glomerular filtration rate (eGFR) associates with higher troponin concentrations. How to interpret hs-cTn results in the presence of these confounding factors re- mains an open question. The aim of this study is to assess whether an integrated prediction model that incorporates hs-cTnT and its confounding factors performs better than hs-cTnT delta threshold alone and to delineate the effect of each confounding factor on the AMI diagnosis. This retrospective cohort study included 17,842 ED patients with serial hs-cTnT measured using a 0h/3h algorithm and eGFR calculated by CKD-EPI creatinine equation at a US medical center. The primary outcome was AMI diagnosis at discharge. Model selection was performed using the logistic regression models of AMI diagnosis with hs-cTnT absolute delta changes and different sets of covariates, which included age, sex, eGFR, and time delta. Model with the smallest Aikaike Information Criteria (AIC) was chosen as the final model, and two-fold cross validation was performed to evaluate model goodness of fit. The area under curve (AUC) of the best fitted model was 0.95. Empirical receiving operating characteristics analysis derived the best probability cutoff of 0.03 for AMI prediction based on a 90% specificity benchmark. The diagnostic performance of this cutoff was compared to that of the hs-cTnT 0h/3h sex-specific delta thresholds we published earlier. The agreement between the predic- tion model cutoff and the sex-specific delta thresholds was 95.8% (Kappa coefficient 0.80). The agreement to true diagnosis was comparable with hs-cTnT sex-specific delta thresholds alone (90.3% agreement, Kappa coeffi- cient 0.32) and with the prediction model cutoff (90.5% agreement, Kappa coefficient 0.33). To further delineate Downloaded from https://academic.oup.com/ajcp/article/158/Supplement_1/S20/6815073 by guest on 11 November 2022