The 2011 outbreak of dengue virus infection in Malwa region of Punjab,India-an evaluation of various diagnostic tests

ObjectiveTo compare the efficacy of rapid immunochromatographic test (ICT) and ELISA for detection of dengue specific parameters (NS1 antigen and IgM antibodies) and the association of these parameters with thrombocytopenia.MethodsA total of 1787 serum samples were obtained from the same number of clinically suspected cases of dengue during an outbreak (2011) of dengue in the Malwa region of Punjab. All the samples were subjected to rapid ICT, dengue early ELISA and dengue IgM-capture ELISA for detection of NS1 antigen and IgM antibodies. Platelet counts of all the cases positive for dengue infection and 150 cases negative for dengue parameters (control group) were recorded.ResutlsRapid ICT for NS1 antigen detection showed same specificity (100%) but lower sensitivity (85.81%) than the dengue early ELISA, while it was 100% and 94.10% respectively for IgM antibody detection. The difference in the platelet counts of cases positive and negative for dengue specific parameters was stastically insignificant (standard error of proportions=0.017, Z value=0.84, P value=0.2).ConclusionsThe confirmation of serological diagnosis of dengue should always be based on ELISA test and ICT and/or thrombocytopenia should not be used as a stand-alone test.     

Diagnosis of Helicobacter pylori infection: non-invasive diagnostic tests

The non-invasive urea breath test can demonstrate the presence of Helicobacter pylori infection with the same accuracy as invasive methods (histology, rapid urease test, culture), but with less distress and inconvenience to the patient. It is evident that this test can and should substitute invasive methods in patients with uncomplicated duodenal ulcer, in those with non-ulcer dyspepsia and in all who have gastrointestinal disorders that do not require endoscopic examination. The urea breath test has a primary role for determining the success of eradication therapy. It is ideal for short- and long-term follow-up, particularly in the case of duodenal ulcer, which is strictly related to the presence of Helicobacter pylori. In serious disease, when endoscopic examination is mandatory, such as complicated ulcer or mucose associated lymphoid tissue lymphoma, the urea breath test can still improve the diagnostic accuracy of Helicobacter pylori infection as it does not imply sampling error, to which biopsy is subject.     

Validity of various diagnostic tests to evaluate cure ofHelicobacter pylori infection

Many diagnostic methods have been developed and used for detectingHelicobacter pylori to evaluate the success of treatment ofH. pylori infection. We investigated and compared the suitability of the rapid urease test (RUT), polymerase chain reaction (PCR),¹³C-urea breath test (¹³C-UBT), and serology with culture for evaluating cure ofH. pylori infection. Forty-sevenH. pylori-positive gastric ulcer patients received dual therapy of lansoprazole (30 mg u.i.d.) and clarithromycin (200 mg b.i.d.). Four weeks after the completion of treatment, RUT, PCR,¹³C-UBT, and culture were performed and the negative rates of these tests were compared. Anti-H. pylori IgG antibodies were measured by enzyme-linked immunosorbent assay (ELISA) before and 4 weeks after completion of the treatment to evaluate changes of titers during the treatment. The negative rate of RUT (55%) was significantly greater than that of culture (27%). Significant declines in titers were seen in the patients who had negative culture results, while the decline in the titer was not significant in the patients who had positive results. PCR assay and¹³C-UBT were suitable for the evaluation ofH. pylori eradication, but RUT was not suitable, because of its sensitivity. By monitoring anti-H. pylori IgG antibody titers, therapeutic failure can be detected early after completion of treatment.     

High circulating levels of the dengue virus nonstructural protein NS1 early in dengue illness correlate with the development of dengue hemorrhagic fever

Infection with any 1 of 4 dengue viruses produces a spectrum of clinical illness ranging from a mild undifferentiated febrile illness to dengue fever (DF) to dengue hemorrhagic fever (DHF), a potentially life-threatening disease. The morbidity and mortality of DHF can be reduced by early hospitalization and careful supportive care. To determine its usefulness as a predictor of DHF, plasma levels of the secreted dengue virus nonstructural protein NS1 (sNS1) were measured daily in 32 children with dengue-2 virus infections participating in a prospective, hospital-based study. Free sNS1 levels in plasma correlated with viremia levels and were higher in patients with DHF than in those with DF. An elevated free sNS1 level (> or =600 ng/mL) within 72 h of illness onset identified patients at risk for developing DHF.     

Antibody-enhanced infection of monocytes as the pathogenetic mechanism for severe dengue illness

Antibody-dependent enhancement of certain virus infections can occur in cells expressing Fc receptors. This mechanism plays an important pathogenetic role in the development of complications associated with dengue virus infection, including dengue hemorrhagic infection and dengue shock syndrome. The virulence of the virus, characterized by the ability to infect Fc receptor-bearing monocytes also influences the development of these severe illnesses.     

Possibilities of using of crystal-optic qualities of bile in early diagnostic stage of cholelithiasis

The aim of our investigation was to study the changes of bile morphology and possibilities of its using in early diagnostic stage of cholelithiasis. We spent the complex investigation of biochemical and crystal-optic qualities of bile in 207 patients with cholelithiasis stage I with different disease duration. The revealed crystal-optic morphotypes have selective morphology due to the bile lithogene level that allows to determine the disease duration and the bile instability to make in-time adequate profilactic.     

Use of dengue NS1 antigen for early diagnosis of dengue virus infection

Accurate and timely diagnosis of dengue virus is important for early detection of dengue virus infection. In this study, the usefulness of the dengue NS1 antigen test was evaluated as a routine, rapid diagnostic test for dengue virus infection. A total of 208 sera from patients suspected of having dengue virus infection were collected and tested for dengue antibody, dengue genome and dengue NS1 antigen. Dengue antibody test, dengue PCR test and dengue antigen test were able to detect dengue virus infection from Days 1 to 8 in 72.8, 52.8 and 44.0% of samples, respectively. Of the 208 sera tested, 69.2% (144/208) of the acute sera were positive for dengue virus infection based on IgM antibody, IgG antibody, NS1 antigen and PCR tests. Thirty-two point two percent of the samples (67/208) were found positive for dengue NS1 antigen, 38.5% (80/208) were PCR positive, 40.9% (85/208) were IgM positive and 36.1% (75/208) were IgG positive for dengue virus. The results reveal the detection rate of dengue virus infection was similar for PCR and dengue antibody (65.9%) and for NS1 antigen and dengue antibody (62.0%) combinations. Therefore, the dengue NS1 antigen test can be used to complement the current antibody test used in peripheral laboratories. Thus, the combination of the NS1 antigen and antibody tests could increase the diagnostic efficiency for early diagnosis of dengue infection.     

Economic impact of dengue illness in the Americas

The growing burden of dengue in endemic countries and outbreaks in previously unaffected countries stress the need to assess the economic impact of this disease. This paper synthesizes existing studies to calculate the economic burden of dengue illness in the Americas from a societal perspective. Major data sources include national case reporting data from 2000 to 2007, prospective cost of illness studies, and analyses quantifying underreporting in national routine surveillance systems. Dengue illness in the Americas was estimated to cost $2.1 billion per year on average (in 2010 US dollars), with a range of $1-4 billion in sensitivity analyses and substantial year to year variation. The results highlight the substantial economic burden from dengue in the Americas. The burden for dengue exceeds that from other viral illnesses, such as human papillomavirus (HPV) or rotavirus. Because this study does not include some components (e.g., vector control), it may still underestimate total economic consequences of dengue.     

Predictive diagnostic value of the tourniquet test for the diagnosis of dengue infection in adults

Objective To examine the accuracy of the admission tourniquet test in the diagnosis of dengue infection among Lao adults. Methods Prospective assessment of the predictive diagnostic value of the tourniquet test for the diagnosis of dengue infection, as defined by IgM, IgG and NS1 ELISAs (Panbio Ltd, Australia), among Lao adult inpatients with clinically suspected dengue infection. Results Of 234 patients with clinically suspected dengue infection on admission, 73% were serologically confirmed to have dengue, while 64 patients with negative dengue serology were diagnosed as having scrub typhus (39%), murine typhus (11%), undetermined typhus (12%), Japanese encephalitis virus (5%), undetermined flavivirus (5%) and typhoid fever (3%); 25% had no identifiable aetiology. The tourniquet test was positive in 29.1% (95% CI = 23.2–34.9%) of all patients and in 34.1% (95% CI = 27.0–41.2%) of dengue‐seropositive patients, in 32.7% (95% CI = 23.5–41.8) of those with dengue fever and in 36.4% (95% CI = 24.7–48.0) of those with dengue haemorrhagic fever. Interobserver agreement for the tourniquet test was 90.2% (95% CI = 86.4–94.0) (Kappa = 0.76). Using ELISAs as the diagnostic gold standard, the sensitivity of the tourniquet test was 33.5–34%; its specificity was 84–91%. The positive and negative predictive values were 85–90% and 32.5–34%, respectively. Conclusions The admission tourniquet test has low sensitivity and adds relatively little value to the diagnosis of dengue among Lao adult inpatients with suspected dengue. Although a positive tourniquet test suggests dengue and that treatment of alternative diagnoses may not be needed, a negative test result does not exclude dengue.     

Diagnosis of immunodeficiency: clinical clues and diagnostic tests

Recognition of immunodeficiency allows steps to be taken to minimize morbidity and mortality. Immunodeficiency can be secondary to viral infection, most importantly secondary to HIV-1 worldwide, medications, disruption of the usual infection clearance mechanisms, or secondary to a myriad of systemic disorders. Immunodeficiency may also be due to one of the growing list of primary immunodeficiency disorders. In infancy, lymphopenia should trigger an evaluation investigating the possibility of severe combined immunodeficiency. Evaluations of children should be done keeping in mind that normal numbers of lymphocytes are higher in children than in adults, immunoglobulin levels in children are lower than in adults in younger age groups, and antibody production in response to polysaccharide antigens is not usually fully developed in the less-than 2-year-old child.     

Noninvasive diagnostic tests for Helicobacter pylori infection in children.

Noninvasive tests can be used for the initial diagnosis of Helicobacter pylori infection and to monitor the success of eradication therapy. In populations with a low prevalence of H. pylori infection (children living in North America and Europe), a high sensitivity is required to make the test valuable for clinical practice. The 13C-urea breath test has been validated in children of different age groups in a significant number of infected and noninfected children in several countries and, thus far, is the only noninvasive test that fulfills sensitivity and specificity quality standards. In studies to date, enzyme immunoassays using monoclonal antibodies to detect H. pylori antigen in stool provide excellent results, but the number of children tested, particularly post-treatment, is not sufficient to recommend the test. All other noninvasive stool tests or methods based on the detection of specific antibodies in serum, whole blood, urine or saliva have limited accuracy in comparison with the 13C-urea breath test. Therefore, these tests cannot be recommended for clinical decision making in pediatric patients.     

Rapid diagnostic tests for dengue and leptospirosis: antibody detection is insensitive at presentation

OBJECTIVE: To determine the performance of rapid diagnostic tests for dengue and leptospirosis that rely on detecting antibodies that may not be produced when patients present for medical treatment. METHODS: We prospectively enrolled 723 patients with undifferentiated febrile illness presenting to rural hospitals in northern and northeastern Thailand over a 1-year period. We evaluated rapid antibody detection diagnostic tests for dengue and leptospirosis on these patients. RESULTS: Sensitivity of the tests was low at the acute visit (7.6-21.5%). Sensitivity at the convalescent visit ranged from 25.8% to 81.5% and was significantly higher than at the acute visit for all tests (chi(2), P < 0.001). CONCLUSIONS: Low sensitivity of the rapid tests at presentation suggests that their utility in the acute phase of dengue and leptospirosis is limited.     

A comparison of diagnostic tests to determine Helicobacter pylori infection

Twenty-five Helicobacter pylori positive and 25 H. pylori negative subjects as defined by culture and phase contrast microscopy of antral biopsy specimens obtained from routine upper endoscopy were studied. Antral biopsies were examined by rapid urease test, phase contrast microscopy, culture and histology. Venous blood was tested for H. pylori specific IgG antibodies by an ELISA technique. Within 7 days of endoscopy the patients also had a [14C]-urea breath test. The sensitivity and specificity of the rapid urease test was 92%, the breath test 96% and 100%, histopathology 96% and 91% and serology 96% and 88%, respectively. The [14C]-urea breath test performed over 1 h with sampling of subjects at 0, 0.5 and 1 h was an accurate and reliable method. Results expressed as counts per minute of the expired 14CO2 proved to be a simple method of assessing H. pylori status. A significant correlation between severity of histological antral gastritis and the amount of 14CO2 expired was observed. This study has shown that the non-invasive 14C-urea breath test and serology are highly sensitive and specific for the diagnosis of H. pylori infection.     

Breath tests as a noninvasive diagnostic method in Helicobacter pylori infection

There are several diagnostic methods for Helicobacter pylori infection, some of them need an endoscopic procedure and biopsy to be performed (invasive) like the rapid urease test, culture and histology. Recently non invasive, specific, sensible, easy to perform and patient's well accepted methods had been developed known as breath test, based on the hydrolysis of labelled urea by Helicobacter pylori urease enzyme, to release ammonia and bicarbonate. Labelled CO2 reaches the bloodstream and the lungs, from where can be collected into the breath for quantification. Labelled urea has to options: 13C stable, non-radioactive and 14C unstable, radioactive. Breath test with 13C is based on the atomic mass difference between 12C and 13C and it is necessary a mass spectrometer and 40 minutes to perform it. Breath test with 14C has 1 uCi (one micro-curie) of radioactivity (1/300 of total radiation received in one year from the environment); the test takes 10 minutes and the samples are read in a beta counter. Both non-invasive tests had demonstrated sensitivity and specificity comparable to established "gold standards" for Helicobacter pylori infection diagnosis.