Hyperglycosylated human chorionic gonadotropin (invasive trophoblast antigen) immunoassay: A new basis for gestational Down syndrome screening.
(65/3575)
BACKGROUND: Serum human chorionic gonadotropin (hCG) and hCG free beta-subunit tests are used in combination with unconjugated estriol and alpha-fetoprotein in the triple screen test, and with the addition of inhibin-A in the quadruple marker test for detecting Down syndrome in the second trimester of pregnancy. These tests have a limited detection rate for Down syndrome: approximately 40% for hCG or free beta-subunit alone, approximately 60% for the triple screen test, and approximately 70% for the quadruple marker test, all at 5%, or a relatively high, false-positive rate. New tests are needed with higher detection and lower false rates. Hyperglycosylated hCG (also known as invasive trophoblast antigen or ITA) is a new test. It specifically detects a unique oligosaccharide variant of hCG associated with Down syndrome pregnancies. We evaluated this new Down syndrome-directed test in prenatal diagnosis. METHODS: Hyperglycosylated hCG was measured in urine samples from women undergoing amniocentesis for advanced maternal age concerns at 14-22 weeks of gestation, 1448 with normal karyotype and 39 with Down syndrome fetuses. RESULTS: The median hyperglycosylated hCG value was 9.5-fold higher in Down syndrome cases (9.5 multiples of the normal karyotype median). The single test detected 80% of Down syndrome cases at a 5% false-positive rate. Urine hyperglycosylated hCG was combined with urine beta-core fragment (urine breakdown product of serum hCG free beta-subunit), serum alpha-fetoprotein, and maternal age-related risk. This urine-serum combination detected 96% of Down syndrome cases at a 5% false-positive rate, 94% of cases at a 3% false-positive rate, and 71% of cases at a 1% false-positive rate. These detection rates exceed those of any previously reported combination of biochemical markers. CONCLUSIONS: Hyperglycosylated hCG is a new base marker for Down syndrome screening in the second trimester of pregnancy. The measurement of hyperglycosylated hCG can fundamentally improve the performance of Down syndrome screening protocols. (+info)
Prospective cross-validation of Doppler ultrasound examination and gray-scale ultrasound imaging for discrimination of benign and malignant pelvic masses.
(66/3575)
OBJECTIVE: To cross-validate, prospectively, the diagnostic performance of established ultrasound methods for discrimination of benign and malignant pelvic masses. METHODS: A total of 173 consecutive women with a pelvic mass judged clinically to be of adnexal origin underwent preoperative ultrasound examination including color and spectral Doppler techniques. A total of 149 tumors were benign, and 24 were malignant. The sensitivity and false-positive rate with regard to malignancy were calculated for the following methods, using cut-off values recommended in previous publications: Lerner score; ultrasound morphology, i.e. tumors without solid components being classified as benign and tumors with solid components as malignant; tumor color score; pulsatility index; resistance index; time-averaged maximum velocity; peak systolic velocity; the combined use of ultrasound morphology and tumor color score and the combined use of ultrasound morphology and peak systolic velocity. Sensitivity and false-positive rate were also calculated for subjective evaluation of the gray-scale ultrasound image and for subjective evaluation of the gray-scale ultrasound image supplemented with subjective evaluation of color Doppler ultrasound examination. The confidence with which the diagnosis was made, based on subjective evaluation, was rated on a visual analog scale. RESULTS: Subjective evaluation of the gray-scale ultrasound image was by far the best method for distinguishing benign from malignant tumors (sensitivity 88%, false-positive rate 4%), followed in descending order by subjective evaluation of the gray-scale ultrasound image supplemented with color Doppler examination, the Lerner score and the time-averaged maximum velocity. Adding Doppler examination to subjective evaluation of the gray-scale image did not increase the number of correct diagnoses, but it increased the confidence with which a correct diagnosis was made in 14% of tumors. In 11 tumors (6% of the series as a whole), the addition of Doppler examination changed the diagnosis based on subjective evaluation of the gray-scale ultrasound image from an incorrect (n = 1) or uncertain (n = 10) diagnosis to a correct and confident diagnosis. CONCLUSION: In experienced hands, subjective evaluation of the gray-scale ultrasound image is the best ultrasound method for discriminating between benign and malignant adnexal masses. The main advantage of adding Doppler examination to subjective evaluation of the gray-scale image is an increase in the confidence with which a correct diagnosis is made. (+info)
Cholecystokinin cholescintigraphy: victim of its own success?
(67/3575)
Numerous publications have reported that a low gallbladder ejection fraction (GBEF) determined by cholecystokinin (CCK) cholescintigraphy has a high positive predictive value for the diagnosis of chronic acalculous cholecystitis (CAC). Clinicians and surgeons have found this test to be clinically useful as an objective method to confirm their clinical diagnosis. However, an abnormally low GBEF is not specific for CAC. For example, numerous other diseases have been associated with a low GBEF, and various therapeutic drugs can cause poor gallbladder contraction. Importantly, improper CCK infusion methodology can result in an erroneously low GBEF. More than one third of healthy subjects and patients who receive sincalide, 0.02 microg/kg infused over 1-3 min, will have an erroneously low GBEF but will have a normal GBEF with a slower infusion (30-60 min) of the same total dose. Because of enthusiastic acceptance of CCK cholescintigraphy by clinicians, the types of patients referred for this test have changed over time. Patients investigated in publications confirming the usefulness of CCK cholescintigraphy had a high pretest likelihood of disease. They underwent extensive workup to rule out other diseases and were followed up for months or years before CCK cholescintigraphy was performed, allowing other diseases to become manifest or symptoms to resolve. However, CCK cholescintigraphy is now being used by clinicians to shorten the workup and follow-up time based on the rationale that CCK cholescintigraphy can quickly confirm or exclude the diagnosis. This new group of referral patients has a lower likelihood of the disease. Many will ultimately be diagnosed with diseases other than CAC. The positive predictive value of this test will likely be lower and the false-positive rate will likely be higher. Nuclear medicine physicians must work to minimize false-positive studies to maintain the confidence of referring clinicians. First, we can educate referring physicians as to the proper use of this study. Next, we must perform CCK cholescintigraphy using optimal methodology that will result in the lowest possible false-positive rate. And finally, we must interpret CCK cholescintigraphy in light of the patient's history, prior workup and clinical setting. (+info)
Performance of indirect immunoglobulin M (IgM) serology tests and IgM capture assays for laboratory diagnosis of measles.
(68/3575)
As progress is made toward elimination of measles, the laboratory confirmation of measles becomes increasingly important. However, both false-positive and false-negative results can occur with the routinely used indirect measles immunoglobulin M (IgM) serology tests. The measles IgM capture assay is considered to be more specific, and therefore, its use is indicated for confirmatory testing, but its relative performance has not been fully assessed. Four commercial indirect measles IgM serology test kits (the Behring, Clark, Gull, and PanBio assays) and a commercial IgM capture assay (the Light Diagnostics assay) were evaluated for their abilities to detect measles virus-specific IgM antibody with a total of 308 serum samples from patients involved in a measles outbreak and with confirmed cases of measles and 454 samples from subjects without measles. The Centers for Disease Control and Prevention (CDC) IgM capture assay was also used in a part of the evaluation. Among the indirect assays, the overall sensitivities ranged from 82.8% (Clark assay) to 88.6% (Behring assay) and specificity ranged from 86.6% (PanBio assay) to 99.6% (Gull assay). These rates were 92.2 and 86. 6%, respectively, for the Light Diagnostics capture assay and 87.0 and 94.8%, respectively, for the CDC capture assay. While the Light Diagnostics capture assay had the best detection rate (80%) with the acute-phase samples compared with those for the rest of the tests (CDC capture assay, 77%; Behring assay, 70%; Gull assay, 69%; PanBio assay, 58%; and Clark assay, 57%), all tests showed a significantly improved sensitivity in the range of 92% (Clark and PanBio assays) to 97% (Light Diagnostics and CDC capture assays) with the convalescent-phase samples, as expected. The best seropositivity rates (in the range of 92 to 100%) were observed with samples collected 6 to 14 days after the onset of symptoms. The Gull assay showed the highest positive predictive value (99.6%), followed by the Behring assay (97.8%) and the CDC capture assay (96.1%). Overall, the Gull and Behring assays were found to be as good as or better than the capture assays. In conclusion, laboratory diagnosis of measles based on IgM serology varies depending on the timing of specimen collection and the test used, and the case for the use of the IgM capture assay as the confirmatory test appears to be uncertain. (+info)
Clinically applicable multiplex PCR for four middle ear pathogens.
(69/3575)
The multiplex PCR method for the detection of Alloiococcus otitidis, Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae (P. H. Hendolin, A. Markkanen, J. Ylikoski, and J. J. Wahlfors, J. Clin. Microbiol. 35:2854-2858, 1997) in middle ear effusions (MEEs) was modified to be better suited for clinical use. To detect false-negative results, an internal amplification was added to the reaction, and to prevent carryover contamination, the dUTP-uracil-N-glycosidase system was incorporated into the procedure. Labor was minimized by using the heat-activatable AmpliTaq Gold polymerase in order to circumvent manual hot start and by detecting the amplification products on an automated sequencer. The performance of the improved protocol was verified with MEEs from patients with otitis media with effusion. In addition, a ligase detection reaction (LDR) was developed for confirmation of the PCR products. The modifications increased the reliability of the protocol and the hands-off time significantly. However, when two DNA extraction protocols were compared, gram-negative bacteria were detected more often in phenol-treated MEEs (94 versus 46%; P < 0.001), and gram-positive bacteria were detected more often in MEEs dissolved in sodium dodecyl sulfate-NaOH-chaotropic salt (83 versus 27%; P < 0.001). The LDR was found to be 100% specific. In all, the results demonstrate the feasibility of the rapid (7-h) multiplex PCR method for routine laboratory use. (+info)
Validation of the INNO-LIA syphilis kit as a confirmatory assay for Treponema pallidum antibodies.
(70/3575)
The commercially available diagnostic tests for syphilis are mostly based on the use of extracted antigens of Treponema pallidum. Pronounced cross-reactivities with other spirochete antigens are often reported. The aim of this study was to validate a novel multiparametric assay (the assay performed with the kit) INNO-LIA Syphilis for the confirmation of syphilis antibodies in a set of 840 documented human serum samples. All serum samples were previously tested at the French World Health Organization reference center for venereal diseases (Institute Alfred Fournier, Paris, France), with a consensus result provided for each sample. The study was conducted in two phases, with each phase involving a validation set (500 well-documented serum samples) and an exploratory set (340 serum samples) of serum samples, respectively. By measuring the sensitivity and specificity, we compared the result of the new assay with the consensus result on the basis of the results of a variable number of classical serological methods and clinical information when available. A sensitivity of 99.6% (95% confidence internal [CI], 98.5 to 99.9%) and a specificity of 99.5% (95% CI, 98.1 to 99.9%) were found for the new line immunoassay. Six of seven samples with indeterminate results by classical serology tested positive with the INNO-LIA Syphilis kit. This single multiparametric assay provides reliable confirmatory diagnostic information that must currently be obtained by the performance and interpretation of results of a combination of serological assays. (+info)
Improved sensitivity of PCR for diagnosis of human granulocytic ehrlichiosis using epank1 genes of Ehrlichia phagocytophila-group ehrlichiae.
(71/3575)
The agent of human granulocytic ehrlichiosis (HGE), Ehrlichia phagocytophila, and Ehrlichia equi probably comprise variants of a single Ehrlichia species now called the Ehrlichia phagocytophila genogroup. These variants share a unique 153-kDa protein antigen with ankyrin repeat motifs encoded by the epank1 gene. The epank1 gene was investigated as an improved target for PCR diagnosis of HGE compared with the currently used 16S rRNA gene target. Primers for epank1 flanking a region that spans part of the 5' ankyrin repeat coding region and part of the unique 3' region were synthesized. Blood samples from 31 patients with suspected HGE who were previously tested by 16S rRNA gene (16S) PCR and indirect immunofluorescent antibody test (IFA) were retrospectively tested with the epank1 primers. Eleven patients were 16S PCR positive and had a seroconversion detected by IFA (group A), 10 patients were 16S PCR negative but had a seroconversion detected by IFA (group B), and 10 patients were 16S PCR negative and seronegative (group C). Ten of the 11 group A patients were epank1 PCR positive, all 10 of the group B patients were epank1 PCR positive, and all of the PCR-negative and seronegative patients (group C) were epank1 PCR negative. The epank1 primers are more sensitive than the previously used 16S rRNA gene primers and therefore may be more useful in diagnostic testing for HGE. (+info)
Diagnosis of human immunodeficiency virus infection using an immunoglobulin E-based assay.
(72/3575)
Immunoglobulin assays that are sensitive and specific for detecting human immunodeficiency virus type 1 (HIV-1) infection are especially important in developing countries where PCR and viral culture may not be readily available. Immunoglobulin E (IgE), which is elevated in HIV-1 infection, is the only antibody that does not cross the placenta, making it potentially valuable for viral detection in both children and adults. This study developed an assay for detection of HIV specific IgE antibodies in adults. A total of 170 serum samples from 170 adults (116 HIV positive and 54 HIV negative) were analyzed. Serum or plasma samples were treated by using the protein G affinity method. The HIV status was determined by using two IgG enzyme-linked immunosorbent assays (ELISAs) and one Western blot evaluation. The IgE enzyme immunoassay test for HIV-1 correctly identified the HIV status in 98.8% of the samples (168 of 170). One false-positive and one false-negative test occurred with the IgE ELISA, as well as with the IgG ELISA test but were correctly identified by the IgE test. Analysis of the data demonstrated a high specificity (99%) and sensitivity (99%) of the IgE test, with 95% confidence intervals. The IgE assay appears to be sensitive and specific, suggesting that IgE-specific antibodies offer an effective method to detect HIV-1 infection in adults. (+info)