Diagnostic Accuracy of a New d-Dimer Assay (Sclavo Auto d-Dimer) for Exclusion of Deep Vein Thrombosis in Symptomatic Outpatients.

In patients presenting non-high clinical pretest probability (PTP), a negative d-dimer can exclude venous thromboembolism without imaging tests. However, each d-dimer assay should be validated in prospective studies. We evaluated an automated d-dimer immunoassay using the Sclavo Auto d-dimer (Sclavo Diagnostics Int, Sovicille, Italy) provided by Dasit Diagnostica (Cornaredo, Milan, Italy). Three hundred two consecutive outpatients suspected of leg deep vein thrombosis (DVT) with non-high PTP were included. The Sclavo Auto d-dimer assay was evaluated on 2 analyzers (Sysmex CA-7000 and Sysmex CS-2100; Sysmex Corporation, Kobe, Japan, provided by Dasit). The cutoff value (200 ng/mL) was established a priori. Prevalence of DVT was 11.9%. Since no false-negative patients were detected, the sensitivity and negative predictive values (NPVs) were 100% (sensitivity = CA-7000: 100% [95% confidence interval, CI: 93.3-100], CS-2100: 100% [95% CI: 93.3-100]; NPV = CA-7000: 100% [95% CI: 97.9-100], CS-2100: 100% [95% CI: 98.0-100]). Specificity was 65.4% (95% CI: 59.4-71.1) and 69.2% (95% CI: 63.3-74.7) for CA-7000 and CS-2100, respectively. Specificity increased when a higher cutoff value (234 ng/mL) was used for patients aged ≥60 years without compromising the safety. Assay reproducibility was satisfactory at concentrations near the cutoff value (total coefficient of variations <10%). In conclusion, the Sclavo Auto d-dimer assay was accurate when used for DVT diagnostic workup in outpatients with non-high PTP. Based on its high sensitivity and NPV, it can be used as a stand-alone test in outpatients with non-high PTP. Given its high specificity, the number of patients in whom further imaging techniques can be avoided increased, improving the yield of the test.

Measurement of factor XIII (FXIII) activity by an automatic ammonia release assay using iodoacetamide blank-procedure: no more overestimation in the low activity range and better detection of severe FXIII deficiencies.

BACKGROUND: Laboratory investigation with specific factor XIII (FXIII) assays plays a crucial role in diagnosis of FXIII deficiency. According to the International Society on Thrombosis and Hemostasis (ISTH), it is necessary a blank sample with iodoacetamide, provided by the kit or locally prepared, when the ammonia release assays are used, to avoid FXIII activity overestimation. METHODS: In this study we set up a modification of the Berichrom FXIII chromogenic assay, in which iodoacetamide was added by the BCS analyzer in the reaction mixture of the blank sample, without modifications of the original reagents. We analyzed 100 plasma samples of outpatients with clinical symptoms suggestive of a bleeding diathesis (20 samples had FXIII activity <20%). RESULTS: In all samples blank subtraction significantly reduced FXIII activity, mostly in the low activity range group (from 10.1% to 2.4%, p<0.0001). In this group correction with iodoacetamide also increased the agreement with the immunoassay and allowed FXIII activity measure up to 0%. CONCLUSIONS: Despite the low number of samples included in the study, the described automatic procedure seemed to decrease FXIII activity overestimation and, especially for low activity range samples (<20%), to improve the agreement between FXIII activity and concentration. Our data suggested that iodoacetamide correction could allow the detection of severe FXIII deficiencies (activity <5%) otherwise undiagnosed using the original method.

A new warfarin dosing algorithm including VKORC1 3730 G > A polymorphism: comparison with results obtained by other published algorithms.

PURPOSE: Warfarin dosing is affected by clinical and genetic variants, but the contribution of the genotype associated with warfarin resistance in pharmacogenetic algorithms has not been well assessed yet. We developed a new dosing algorithm including polymorphisms associated both with warfarin sensitivity and resistance in the Italian population, and its performance was compared with those of eight previously published algorithms. METHODS: Clinical and genetic data (CYP2C9*2, CYP2C9*3, VKORC1 -1639 G > A, and VKORC1 3730 G > A) were used to elaborate the new algorithm. Derivation and validation groups comprised 55 (58.2% men, mean age 69 years) and 40 (57.5% men, mean age 70 years) patients, respectively, who were on stable anticoagulation therapy for at least 3 months with different oral anticoagulation therapy (OAT) indications. RESULTS: Performance of the new algorithm, evaluated with mean absolute error (MAE) defined as the absolute value of the difference between observed daily maintenance dose and predicted daily dose, correlation with the observed dose and R(2) value, was comparable with or slightly lower than that obtained using the other algorithms. The new algorithm could correctly assign 53.3%, 50.0%, and 57.1% of patients to the low (≤25 mg/week), intermediate (26-44 mg/week) and high (≥ 45 mg/week) dosing range, respectively. Our data showed a significant increase in predictive accuracy among patients requiring high warfarin dose compared with the other algorithms (ranging from 0% to 28.6%). CONCLUSIONS: The algorithm including VKORC1 3730 G > A, associated with warfarin resistance, allowed a more accurate identification of resistant patients who require higher warfarin dosage.

Evaluation of a new automated panel of assays for the detection of anti-PF4/heparin antibodies in patients suspected of having heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin treatment; the prognosis depends on early and accurate diagnosis, and prompt start of alternative anticoagulants. Because of high sensitivity, the commercially available immunologic assays are widely used, though not suited to be run on single samples and with a turnaround time of 2-3 hours. We evaluated two new, rapid, automated, semi-quantitative chemiluminescent immunoassays in HIT suspected patients: HemosIL AcuStar HIT-IgG(PF4-H) (specific for IgG anti-PF4/heparin antibodies) and HemosIL AcuStar HIT-Ab(PF4-H) (detecting IgG, IgM and IgA anti-PF4/heparin antibodies) (both from Instrumentation Laboratory). A total of 102 patients with suspected HIT were included; HIT was diagnosed in 17 (16.7%). No false negative cases were observed using either the HemosIL AcuStar HIT-IgG(PF4-H) or the HIT-Ab(PF4-H) assay (sensitivity and negative predictive values = 100%; negative likelihood ratios <0.01). The specificity was higher for the HemosIL AcuStar HIT-IgG(PF4-H) in comparison with that of the HemosIL AcuStar HIT-Ab(PF4-H) (96.5% vs. 81.2%). Higher values of the HemosIL AcuStar HIT-IgG(PF4-H) were associated with increased probability of HIT. Patients with confirmed HIT and thrombotic complications had significantly higher levels of HemosIL AcuStar HIT-IgG(PF4-H) than those without thrombotic complications. The HemosIL AcuStar HIT-IgG(PF4-H) and HIT-Ab(PF4-H) assays showed a very high sensitivity, and therefore they can reliably be used to rule out HIT in suspected patients. The diagnostic specificity was greatly increased by using the HemosIL AcuStar HIT-IgG(PF4-H). Both the assays are reproducible (CVs <6%), rapid (turnaround time 30 minutes), automated, and semi-quantitative, and they can be run for single sample testing.