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.

Analysis of agreement between Duplex ultrasound scanning and arteriography in patients with lower limb artery disease.

BACKGROUND: Angiography is the gold standard for therapeutic decision-making in lower limb artery disease. However, both the potentiality and safety of Duplex ultrasound scanning suggest that it may become the main diagnostic tool. The present study aimed to investigate the agreement between Duplex scanning and angiography in the diagnosis of stenosis in lower limb artery disease. METHODS: Forty-nine patients with lower limb artery disease (24 claudication, 12 critical ischemia, 13 skin lesions) underwent angiography and Duplex scanning. The lower limb arterial axis was divided into 15 segments and graded on the basis of the degree of stenosis (0-49%, 50-69%, 70-99% and occlusion). Agreement between angiography and Duplex scanning was assessed by Cohen's kappa statistics (kappa). The sensitivity and specificity of Duplex scanning in detecting significant stenosis at angiography (>/= 70%) were also calculated. RESULTS: Good diagnostic agreement (kappa = 0.70; 95% CI 0.588-0.825) was achieved in the whole arterial axis. Agreement was good for the aorto-iliac district (kappa = 0.63) with a sensitivity of 63% and a specificity of 96%, and for the femoro-popliteal district (kappa = 0.70) with a sensitivity of 74% and a specificity of 83%. In infrapopliteal arteries, kappa showed a poor agreement, but Duplex scanning detected 28 patent tibial arteries in limbs that were not opacified on arteriography. CONCLUSIONS: Duplex scanning shows good agreement with angiography in lower limb artery disease on the whole, but poor agreement in infrapopliteal districts, with a low sensitivity and high specificity in detecting significant stenoses or occlusions.