Correct Negative Results Research Articles

Point of Care Method for the Determination of Dabigatran in Urine Samples From Patients On Treatment.

AbstractAbstract 2270Dabigatran is effective and safe for prevention of thromboembolism in several indications at daily fixed doses not requiring laboratory dose adjustment. However, it may be necessary to determine its activity/concentration in specific patient populations by specific assays from plasma samples. A point of care (POC) method may offer advantages by providing immediate results to facilitate medical decisions for acute therapeutic interventions.Plasma and urine samples were taken from patients on treatment with 110mg or 150mg dabigatran bid (n=110) and healthy persons (n=144) after having given written informed consent. Dabigatran was purified from commercially available Pradaxa® and its purity was characterized by analytical methods and S2238 thrombin specific chromogenic substrate assay and Hemoclot assay containing dabigatran standards. The S2238 assay was also used for the determination of dabigatran in plasma samples of patients and healthy persons using one purified dabigatran as standard. The lower limit of detection was 0.06μg/ml plasma. In urine dabigatran was determined by a POC method incubating the lyophilized reagents on mini-strips followed by incubation with patient‘s urine (international patent application No PCT/EP2012/002540). The development of colour of urine samples was determined 10 min after incubation with reagents quantitatively by optical density (OD) measurement and qualitatively as judged by eye according negative and positive colour (three independent readings by SD, SK, CG, and photographic documentation). To determine the positive and negative predictive value (PPV and NPV) of plasma samples, a cutoff value of <0.06μg/ml dabigatran was defined. The PPV and NPV of POC method was determined for urine samples of the control and treatment group according positive and negative development of colour as judged by eye reading.Control persons (n=144) displayed plasma concentrations of 0.04+0.03 μg/ml (mean, standard deviation) of whom 128 had values below the cutoff value <0.06 μg/ml. Sixteen patients had values above this cutoff. Accordingly, the NPV for correct negative results in controls was 88.9%. In patients on therapy the concentration of dabigatran was 0.12+0.08 μg/ml (n=107). 102/107 patients had plasma concentrations of dabigatran above the cutoff value of 0.06 μg/ml and 5 patients below the cutoff-value. This results in a PPV of 95.4%. Using the POC method for dabigatran in urine all of 144 control persons had negative values with OD measurement (0.803+0.116 OD units) and eye measurement. The NPV for control persons was 100%. During therapy with dabigatran, all 110 patients had positive colour development as judged by eye corresponding to an OD of 0.219+0.161. Accordingly, the PPV was 100% for patients on treatment with dabigatran. Limitations of the POC methods are the lack of information about the compliance of the patient and severe renal impairment. The validation of the POC assay by patients is ongoing.The POC method of patients on treatment with dabigatran improves the NPV and PPV from about 90% with plasma samples to 100% using urine samples, respectively. The method is non-invasive, rapid, and specific, can be repeatedly performed and may be used by medical personal and patients. The development of colour is different from the POC method for rivaroxaban. Disclosures:No relevant conflicts of interest to declare.

External quality assessment of platelet serology and human platelet antigen genotyping: a 10‐year review

In this review, the results of an external quality assessment (EQA) over 10 years of platelet (PLT) serology and of human platelet antigen (HPA) polymorphisms genotyping are shown. The detection and identification of PLT antibodies and the distinction between PLT-specific antibodies and HLA Class I antibodies are evaluated. Each year, serum samples from five patients and four donor blood samples for DNA typing were distributed. Laboratories could participate as a screening laboratory (SL; n = 7) or as an identification laboratory (IL; n = 8). SLs scored 57 to 100 percent correct positive and 91 to 100 percent correct negative results in the detection of PLT-specific antibodies. SLs only using a PLT immunofluorescence test (PIFT) scored less well than those using a PLT glycoprotein-based antibody detection method. ILs scored 70 to 100 percent correct positive and 87 to 100 percent correct negative results for, respectively, the detection and identification of PLT-specific antibodies. Both the specificity and the sensitivity for the detection and identification of PLT-specific antibodies were not as good in ILs using solid-phase enzyme-linked immunosorbent assay methods as in those using the monoclonal antibody immobilization of PLT antigens (MAIPA) assay. For HPA-1, -2, -3, and -5 genotyping, incorrect results were observed only twice in 280 genotyping assays. The data underscore the necessity of using the most accurate methods with a high level of knowledge, experience, and technical training. For screening purposes, it is not sufficient to use only the PIFT, whereas for identification of PLT-specific antibodies, the MAIPA assay is the superior assay.

Accuracy of the “Triple Test” in the Diagnosis of Palpable Breast Masses in Saudi Females

For patients who present to clinicians with palpable breast lesions, the triple test: (physical examination, mammography and fine-needle aspiration cytology) can be employed to provide accurate diagnosis. In this study, the sensitivity, specificity and predictive values of triple test components were studied separately and in combination. During the study period (from January 1998 to December 1999), 140 patients with palpable breast masses were subjected to all components of the triple test followed by confirmatory open biopsy. Physical examination showed 82.6% sensitivity, 97.3% specificity and 86.4% positive predictive value. Mammography showed 87.5% sensitivity, 97.3% specificity and 87.5% positive predictive value and fine-needle aspiration cytology (FNAC) showed 91.7% sensitivity, 100% specificity and 100% positive predictive value in concordant cases (elements had either all malignant or all benign results). The triple test was 100% accurate in the diagnosis of palpable breast lesions when all three elements were concordant. Based on these results, we recommend elimination of the confirmatory open biopsy, which will result in reduced expenses and morbidity compared with open biopsy.

Possibility of Improving the Acceptance Rateof Early Detection Testing for Prostate Cancerwith a One-Step Test for Prostate-Specific Antigen in Whole Blood

In order to increase the acceptance rate of early detection testing for prostate cancer, a qualitative prostate-specific antigen (PSA) one-step test has been developed. Determining the PSA level with this test system takes 10 min. The blood samples of 190 men were tested in this qualitative assay, which uses 50 μl of EDTA whole blood and in which the results are ascertained visually. Parallel samples were tested in serum-based, quantitative assays (Abbott Imx, EIA). The findings of the two kinds of assays were compared and evaluated regarding their correspondence (<4.0 and ≥4.0 ng/ml). For the 74 blood samples in which the quantitative assay showed PSA levels <4.0 ng/ml, the PSA one-step test showed 83.8% correct negative results (corresponds to diagnostic specificity). For the 116 samples in which the classic assay showed PSA levels ≥4.0 ng/ml, the one-step test showed 90.5% correct positive results (sensitivity). The noted deviations appear especially around the cut-off value of 4.0 ng/ml, i.e. within the PSA concentration range of 3.0 < 4.0 and 4.0 < 5.0 ng/ml. The qualitative PSA one-step test presented here demonstrates good reproducibility. It can be conducted by the patient and is easy to use. The test offers a simple, feasible method for early detection programs for prostate cancer.

Identification of Candida albicans and C. tropicalis with an umbelliferyl-labelled galactosaminide.

The 4-methylumbelliferyl-N-acetyl-beta-D-galactosaminide (UAG) test was evaluated in parallel with chlamydospore (CHL) and germ-tube (GT) tests for the identification of Candida spp. The UAG test gave 86.6% correct identification of C. albicans and C. tropicalis. Non-C. albicans and non-C. tropicalis yeasts gave correct negative results in UAG tests. Only one isolate of Trichosporon beigelii gave a "false" positive reaction. The UAG test, which can be completed within 30 min, is a reliable test for screening non-C. albicans and non-C. tropicalis yeasts.

Cell electrophoresis for diagnostic purposes. I. Diagnostic value of the electrophoretic mobility test (EMT) for the detection of gynaecological malignancies.

Lymphocytes from 278 gynaecological patients (100 controls and 178 patients with a malignant condition) have been investigated for their response to encephalitogenic factor, cancer basic protein, and KCl extract of adenocarcinoma of the body of the uterus as "antigens", using tanned sheep erythrocytes ETS as indicator particles in the electrophoretic mobility test (EMT). Electrophoretic mobility was measured with a Zeiss cytopherometer. The study was split into three test series producing in the cancer group 66% correct positive test results (34% false negatives) and in the control group 83% correct negative results (17% false positives). Consequently, with the instrumentation used, EMT is, at least in our hands, not sufficiently reliable for the diagnosis of cancer.

A Simple and Sensitive Nonradioactive Method for the Detection of Urinary Human Chorionic Gonadotropin and Diagnosis of Early Human Pregnancy. I. Multiple-unit Test

A simple, sensitive, and reproducible method for the detection of urinary human chorionic gonadotropin (hCG) and diagnosis of early human pregnancy is reported. A 5-ml aliquot of filtered early-morning urine sample was concentrated in a microconcentrator (M) to 0.1 ml of retentate which was diluted with 0.4 ml of distilled water and tested in a hemagglutination inhibition test (M-HIT). Also, a 0.1-ml aliquot of filtered unconcentrated urine sample was diluted with 0.4 ml of distilled water and tested in the same hemagglutination inhibition test (HIT). Urine samples from women of reproductive age; from perimenopausal, menopausal, and proteinuric women; and from adult males were tested in the HIT and M-HIT. Some of these urine samples were also tested in the mouse ovulation bioassay (MOB). The M-HIT was significantly more reliable than the HIT for diagnosis of early pregnancy 25 to 55 days after menses. Correct negative results with the M-HIT were obtained in urine samples of most of the nonpregnant cycling, perimenopausal, and menopausal women, and adult males. Urine samples from subjects with severe proteinuria gave false-positive types of reactions in the M-HIT. Positive results were obtained in the MOB with a number of urine samples from pregnant, perimenopausal, and menopausal women. A properly conducted M-HIT should be very valuable in diagnosing pregnancy as early as the 26th day of the cycle in regularly menstruating women.