Enzyme immunoassay (EIA) in the rapid diagnosis of gonorrhoea

The diagnostic value of a new, modified enzyme immunoassay (EIA) (Gonozyme; Abbott Laboratories, North Chicago III) was evaluated for the rapid antigenic detection of Neisseria gonorrhoeae in endocervical and urethral specimens. EIA results were compared with those of Gram stain (GS) and conventional culture tests. EIA sensitivity and specificity for male patients attending dermatovenerological clinic were 100% and 96.8% respectively in comparison to 86.7% and 96.8% obtained by Gram staining. For female Obstetrics-Gynaecology patients EIA sensitivity of 100% was highly significant compared to 50% sensitivity by the Gram stain. In culture, 30 strains of N. gonorrhoeae were isolated from 125 male specimens and 2 from 105 specimens from females; this suggests a prevalence of N. gonorrhoeae of 24% in males and 1.9% in females. In vitro antibiotic sensitivity testing indicated 55% resistance to penicillin and 43% to ampicillin in these isolated strains; all were sensitive to erythromycin/tetracycline. 12% of the strains were beta-lactamase producers.     

Comparison of Diagnostic Methods in the Evaluation of Onychomycosis

Onychomycosis is a common nail problem, accounting for up to half of all nail diseases. Several nail disorders may mimic the onychomycosis clinically. Therefore, a sensitive, quick, and inexpensive test is essential for screening nail specimens for the administration of the proper drug. The aim of this study was to compare 4 different diagnostic methods in the evaluation of onychomycosis and to determine their sensitivity, specificity, positive predictive value, and negative predictive value. In a cross-sectional study, nail specimens were collected from 101 patients suspected to have onychomycosis during a 14-month period. The nail specimens were examined using potassium hydroxide (KOH) 20 %, KOH-treated nail clipping stained with periodic acid-Schiff (KONCPA), and calcofluor white (CFW) stain, and grew a fungal culture. The culture was chosen as the gold standard for statistical analysis using the McNemar and chi-square tests. Out of 101 patients, 100 (99 %) patients had at least 1 of the 4 diagnostic methods positive for the presence of organisms. The positive rates for the fungal culture, KOH preparation, CFW, and KONCPA were 74.2, 85.1, 91.09, and 99.01 %, respectively. The sensitivity and negative predictive value of KONCPA was 100 %. KONCPA was the most sensitive among the tests and was also superior to other methods in its negative predictive value. KONCPA was easy to perform, rapid, and gave significantly higher rates of detection of onychomycosis compared to the standard methods of KOH preparation and fungal culture. Therefore, KONCPA should be the single method of choice for the evaluation of onychomycosis.     

Resistance to Gonorrhea Possibly Mediated by Bacterial Interference

Two men with no prior history of urethritis failed to develop gonorrhea after sexual exposures to women with genital gonococcal infection. Usual methods of prophylaxis, such as antibiotics or condoms, were not employed. The aerobic bacterial flora of these men's urethras consisted of several bacteria, some of which inhibited the in vitro growth of Neisseria gonorrhoeae. The hypothesis is suggested that bacterial interference may have played a role in protecting these men from gonorrhea.     

探讨UF-100在泌尿系统感染诊断中的应用价值

为探讨UF-100尿液分析在泌尿系统感染诊断中的临床应用价值,对UF-100作重复性试验,用UF- 100检测760份尿中细菌和白细胞,同时作定量细菌培养并将结果作比较。用Yerushalmy模式评价2种方法的一致性及UF-100筛检的灵敏度、特异性等。重复试验中,UF-100细菌计数CV值低于细胞计数CV,与定量细菌培养结果比较,细菌计数的筛检灵敏度为80.0%,特异性为50.4%,阳性预计值为28.7%,阴性预计值为91.0%,假阳性率为39.7%,假阴性率为4.0%,准确率为56.3%。UF-100具有良好的分析尿液的性能,在临床尿路感染筛检时可用细菌一项指标,90%结果阴性的标本可在短时间内筛去,大大减少实验人员繁复劳动,降低检验成本,但应注意假阴性,更不可替代尿定量细菌培养。     

Comparison of two different stool antigen tests for the primary diagnosis of Helicobacter pylori infection in turkish patients with dyspepsia

AIM: To assess the reliability of two different enzyme immunoassays in detecting the Helicobacter pylori status in stool specimens of Turkish patients with dyspepsia. MATERIALS AND METHODS: One hundred and fifty-one patients [74 with nonulcer dyspepsia (NUD), 64 with duodenal ulcer (DU) and 13 with gastric cancer] who were admitted to the endoscopy unit of Istanbul University, Cerrahpasa Medical Faculty for upper gastrointestinal endoscopy because of dyspepsia were enrolled in the study. Helicobacter pylori infection was confirmed in all patients by histology, rapid urease test and culture. A patient was classified as being H. pylori-positive if the culture alone or both the histology and the rapid urease test were positive and as negative only if all of these tests remained negative. Stool samples were obtained from patients to assess the reliability of a monoclonal (FemtoLab H. pylori) and a polyclonal (Premier Platinum HpSA) stool antigen test and to compare the diagnostic accuracies of these two tests. A chi2 test was used for statistical comparisons. RESULTS: Using cut-off values of 0.19 for FemtoLab H. pylori and 0.16 for Premier Platinum HpSA, the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were 93%, 90%, 98%, 68% and 93% for the monoclonal test and 84%, 67%, 94%, 40% and 81% for the polyclonal test, respectively. The sensitivity, specificity, negative predictive value and diagnostic accuracy of the monoclonal test were significantly greater than those of the polyclonal test (chi2 = 3.98; p < .05 for sensitivity and chi2 = 15.67; p = .000 for specificity, chi2 = 15.78; p = .000 for negative predictive value and chi2 = 6.37; p = .012 for diagnostic accuracy). The bacterial load did not affect the sensitivity of either test. CONCLUSIONS: The monoclonal FemtoLab H pylori test, using a cut-off 0.19, is a very sensitive, specific and easy to perform diagnostic tool for the primary diagnosis of H. pylori infection in Turkish patients with dyspepsia.     

Evaluation of Cobas Amplicor MTB test to detect Mycobacterium tuberculosis in pulmonary and extrapulmonary specimens

Tuberculosis (TB) is one of the major public health problems in the world. Effective control of TB depends on rapid and correct diagnosis and appropriate treatment. The aim of this study was to evaluate the performance of Cobas Amplicor MTB (CA-MTB) test for pulmonary and extrapulmonary specimens isolated in our laboratory. A total of 424 specimens obtained from the suspected TB patients from January 2003 to August 2004 were included in this study. All specimens (173 pulmonary and 251 extrapulmonary specimens) were processed, stained, cultured and assayed using the CA-MTB test for identification of Mycobacterium tuberculosis. The CA-MTB test results were compared to culture and acid-fast staining as gold standard. The sensitivity, specificity, positive and negative predictive values of CA-MTB were determined as 73%, 100%, 100%, and 97% for pulmonary specimens, and 45%, 100%, 100% and 96% for extrapulmonary specimens respectively. The sensitivity of the test for acid-fast bacilli (AFB) smear positive pulmonary and extrapulmonary specimens was 92% and 75%. These results indicate that the CA-MTB is a rapid test for detection of tuberculosis in pulmonary specimens, but does not perform well enough in extrapulmonary specimens.     

流感快检法与病毒分离法检测结果的比较

实验中用流感快检法和病毒分离法同时对61份标本进行检测,并进行了比较,快检法的阳性预测值为100%,阴性预测值为40.9%,两种方法的符合率为57.3%。结果表明,快检方法可以作为快速的辅助手段。     

降钙素原、IL-6及CRP诊断新生儿宫内细菌感染的临床价值

目的:探讨降钙素原、IL-6及CRP对新生儿宫内细菌感染诊断的临床价值。方法:采用回顾性分析方法,对121例疑似宫内细菌感染的新生儿的相关临床资料进行比较分析。通过影像学或细菌学方法对患儿进行检查判定感染类型,并检测患儿脐血中的降钙素原、C-反应蛋白(CRP)和白细胞介素-6(IL-6)的水平。结果:在121例患儿中41例确定为细菌感染,IL-6(100ng/L)与CRP(10mg/L)联合对诊断新生儿宫内细菌感染的敏感性为90.1%,特异性为76.9%,阴性预测率为91.7%,阳性预测率为71.9%;与PCT结合后,诊断新生儿宫内细菌感染的敏感性升高至98.3%,特异性为67.8%,阴性预测率为99.2%,阳性预测率为57.0%。结论:脐血PCT可作为新生儿宫内细菌感染诊断的有效指标,可明显提高IL-6与CRP诊断新生儿宫内细菌感染的阴性预测值和敏感性,指导临床治疗。     

The Role of Glutamate Dehydrogenase (GDH) Testing Assay in the Diagnosis of Clostridium difficile Infections: A High Sensitive Screening Test and an Essential Step in the Proposed Laboratory Diagnosis Workflow for Developing Countries like China

The incidence and severity of Clostridium difficile infection (CDI) in North America and Europe has increased significantly since the 2000s. However, CDI is not widely recognized in China and other developing countries due to limited laboratory diagnostic capacity and low awareness. Most published studies on laboratory workflows for CDI diagnosis are from developed countries, and thus may not be suitable for most developing countries. Therefore, an alternative strategy for developing countries is needed. In this study, we evaluated the performance of the Glutamate Dehydrogenase (GDH) test and its associated workflow on 416 fecal specimens from suspected CDI cases. The assay exhibited excellent sensitivity (100.0%) and specificity (92.8%), compared to culture based method, and thus could be a good screening marker for C. difficile but not for indication of toxin production. The VIDAS CDAB assay, which can detect toxin A/B directly from fecal specimens, showed good specificity (99.7%) and positive predictive value (97.2%), but low sensitivity (45.0%) and negative predictive value (88.3%), compared with PCR-based toxin gene detection. Therefore, we propose a practical and efficient GDH test based workflow strategy for the laboratory diagnosis of CDI in developing countries like China. By applying this new workflow, the CDI laboratory diagnosis rate was notably improved in our center, yet the increasing cost was kept at a minimum level. Furthermore, to gain some insights into the genetic population structure of C. difficile isolates from our hospital, we performed MLST and PCR toxin gene typing.     

Trichomonas vaginalis detection using real-time TaqMan PCR

1978 women and 93 men, all suspected of having a Trichomonas vaginalis infection, were tested for the presence of T. vaginalis by real-time PCR using the T. vaginalis-specific 2-kb repeated sequence, and by direct microscopy and culture. 40 samples were positive by T. vaginalis real-time PCR and 27 were positive by wet mount microscopy, either direct or after culture. All samples positive by direct microscopy of culture were also positive by real-time PCR. Of the 13 samples which were real-time PCR positive but negative by direct microscopy and culture 11 were confirmed by another T. vaginalis real-time PCR based on the beta tubulin gene. Only 2 samples (0.1%) showed inhibition in the PCR. The prevalence of T. vaginalis infection in the female patients was 1.8%. The sensitivity, specificity, positive and negative predictive values of the real-time PCR were 100%, 99.9%, 95% and 100%, respectively. The same test characteristics for the combined conventional T. vaginalis detection methods (microscopy+culture) were 71%, 100%, 100% and 99%, respectively. Therefore, real-time PCR is the method of choice for the diagnosis of T. vaginalis infection.     

Development and evaluation of a PCR method for diagnosis of Salmonella enteric fever, based on DNA sequences of the hilA gene

Typically, diagnosis of enteric fever due to Salmonella spp. is by bacterial isolation from blood culture; however, the blood culture method is slow, not always available, and not informative in patients with antibiotic treatment. Salmonella spp. uses the hilA gene (component of the pathogenicity island I) to invade epithelial cells and produce infection. Using the hilA gene sequence a PCR test was designed to detect Salmonella in blood samples. The sensitivity (S), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) of the PCR method were obtained by testing the blood samples from 34 patients with suspected of enteric fever. Presence of S. typhi was confirmed by blood culture. Blood samples were also tested from 35 patients with infections due to other non-Salmonella pathogens, again corroborated by blood culture (Klebsiella pneumoniae, 9; Serratia marcescens, 5; Escherichia coli, 4; Pseudomonas aeruginosa, 9; Providencia alcalifaciens, 4; Enterobacter cloacae, 4). Control samples were obtained from 150 healthy volunteers. The S, SP, PPV and NPV for the PCR method were all 100%. The lowest number of colony forming units/ml detected by PCR in blood samples was 10.     

Helicobacter pylori stool antigen test in patients with bleeding peptic ulcers

BACKGROUND: Helicobacter pylori has been linked to chronic gastritis, peptic ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma. Invasive tests are less sensitive than noninvasive tests in diagnosing H. pylori infection in patients with bleeding peptic ulcers. The H. pylori stool antigen test has been useful in diagnosing H. pylori in patients with peptic ulcers before and after eradication of H. pylori. The aim of this study was to evaluate the H. pylori stool antigen test in patients with bleeding peptic ulcers. METHODS: Patients with bleeding and nonbleeding peptic ulcers underwent a rapid urease test, histology, bacterial culture and H. pylori stool antigen test. Positive H. pylori infection was defined as a positive culture or both a positive histology and a positive rapid urease test. Helicobacter pylori stool antigen was assessed with a commercial kit (Diagnostec H. pylori antigen EIA Kit, Hong Kong). RESULTS: Between October 2000 and April 2002, 93 patients with bleeding peptic ulcers (men/women: 78/15, gastric ulcer/duodenal ulcer: 58/35) and 59 patients with nonbleeding peptic ulcers (men/women: 47/12, gastric ulcer/duodenal ulcer: 30/29) were enrolled in this study. Forty-seven (50.5%) patients with bleeding peptic ulcers and 30 (50.8%) patients with nonbleeding peptic ulcers, were found to be infected with H. pylori (p > .1). Helicobacter pylori stool antigen tests were positive in 54 (58.1%) and 30 (50.8%) patients with bleeding peptic ulcers and nonbleeding peptic ulcers, respectively (p > .1). The sensitivity (82% vs. 93%), specificity (68% vs. 93%), positive predictive value (74% vs. 93%), negative predictive value (77% vs. 93%) and diagnostic accuracy (75% vs. 93%) were all lower in patients with bleeding vs. nonbleeding peptic ulcers. The specificity, positive predictive value, and diagnostic accuracy of the H. pylori stool antigen test in patients with bleeding peptic ulcers were significantly lower than those in patients with nonbleeding peptic ulcers (p = .01, p = .02 and p = .003, respectively). CONCLUSION: The H. pylori stool antigen test is not reliable for diagnosing H. pylori infection in patients with bleeding peptic ulcers.     

Comparison of a modified shell vial culture procedure with conventional mouse inoculation for rabies virus isolation

Rabies is a neurotropic disease that is often lethal. The early diagnosis of rabies infection is important and requires methods that allow for the isolation of the virus from animals and humans. The present study compared a modified shell vial (MSV) procedure using 24-well tissue culture plates with the mouse inoculation test (MIT), which is considered the gold standard for rabies virus isolation. Thirty brain samples (25 positive and 5 negative by the fluorescent antibody test) obtained from different animal species at the National Institute of Hygiene Rafael Rangel in Caracas, Venezuela, were studied by the MIT and MSV assays. Nine samples (36%) were positive at 24 h, 10 (40%) were positive at 48 h and six (24%) were positive at 72 h by the MSV assay. With the MIT assay, 76% were positive at six days post inoculation and 12% were positive at 12 and 18 days post inoculation. One sample that was negative according to the MSV assay was positive with MIT on the 12th day. The MSV procedure exhibited a sensitivity of 96.2%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value 80%. This procedure allowed for rapid rabies virus detection. MIT can be employed as an alternative method in laboratories without tissue culture facilities.     

Immunodiagnosis of sexually transmitted disease

Methods for detecting microbial antigens in clinical specimens offer an alternative to culture in the diagnosis of some sexually transmitted diseases. Developers of the immunologic methods are faced with a number of problems in evaluating the new tests. Traditionally, these tests are compared to culture as the "gold standard." Unfortunately, culture for Neisseria gonorrhoeae or Chlamydia trachomatis--the two agents most commonly sought--is considerably less sensitive than 100 percent. Immunologic methods may appear to produce false positives when the paired specimens are actually false-negative cultures. Another source of discordant results is sampling variation. These considerations, however, will not account for all false-positive results. Even the best non-culture methods have a low rate of false-positive results. If a new test has a specificity of 97 percent, it, by definition, yields approximately 3 percent false-positive reactions. In low-prevalence settings this false-positive rate will create problems in interpreting the results. For example, in a population with 3 percent prevalence of infection, a positive result in a 97 percent specificity test could only have a predictive value of 50 percent. Most testing for STD agents is performed in low-prevalence settings. None of the currently available immunodiagnostic procedures has a performance profile that suggests it will be satisfactory for diagnostic use in the low-prevalence setting.     

血清PCT、CRP及IL-6联合检测诊断细菌性血流感染的临床价值分析

目的:探讨血清降钙素原(PCT)、C反应蛋白(CRP)及白介素-6(IL-6)联合检测诊断细菌性血流感染(BSI)的临床价值。方法:选取我院2015年8月到2016年10月收治的疑似细菌性BSI患者216例,入院后均送检血培养,根据培养结果将其分为阳性组(102例)和阴性组(114例)。统计细菌性BSI阳性率、革兰阳性菌感染率和革兰阴性菌感染率;检测血清PCT、CRP、IL-6水平,并比较两组患者的差异,同时绘制ROC曲线并计算出各指标及联合检测的灵敏度、特异度、阳性预测值、阴性预测值及约登指数值。结果:所有疑似BSI患者的细菌阳性检出率为47.22%,革兰阳性菌感染率与革兰阴性菌感染率对比无差异(P0.05);阳性组的血清PCT、CRP、IL-6水平均明显高于阴性组(P0.05);血清IL-6的AUC明显大于PCT和CRP(P0.05);PCT、CRP及IL-6联合检测的灵敏度、特异度、阳性预测值、阴性预测值及约登指数均明显高于单项检测(P0.05)。结论:血清PCT、CRP及IL-6对于BSI均有着一定诊断价值,而各指标联合检测诊断BSI的临床价值更高。     

实时荧光核酸恒温扩增技术 在检测分泌物中MRSA的应用

目的对实时荧光核酸恒温扩增技术(simultaneous amplification and testing method,SAT)检测创面分泌物中耐甲氧西林金黄色葡萄球菌(MRSA)核酸试剂盒(RNA恒温扩增)应用进行评价。方法收集我院临床各科室于2016年12月至2017年1月送至检验科微生物室347份分泌物标本,分别用实时恒温扩增技术和ChromID MRSA产色平板筛选MRSA。当SAT法和MRSA培养结果不相符时,进行冻存的备用标本PCR扩增、第三方测序,以MRSA培养结果加PCR测序结果作为本次试验"扩大金标准",计算SAT的灵敏度、特异性、阳性预测值、阴性预测值,并进行相应的统计学分析。结果以ChromID MRSA产色平板筛选加PCR测序作为"扩大金标准",SAT法检测MRSA的敏感度为90.91%、特异度为99.40%、阳性预测值为83.33%、阴性预测值为99.40%,对MRSA的最低检出下线为102拷贝/mL,Kappa系数为0.85。结论 SAT技术在检测分泌物中MRSA具有很高的灵敏度、特异性,而且准确、可靠,与传统的细菌培养相比耗时短,为MRSA的实验室诊断提供新的检测方法。     

Detection of Chlamydia trachomatis in pregnant women by the Papanicolaou technique, enzyme immunoassay and polymerase chain reaction

OBJECTIVE: To compare Papanicolaou staining, enzyme immunoassay (EIA) and the polymerase chain reaction (PCR) techniques for detecting Chlamydia trachomatis in pregnant women. STUDY DESIGN: Endocervical specimens were taken randomly from 125 pregnant women with or without symptoms. These women attended their first medical consultation at the Regional General Ignacio Zaragoza Hospital. Samples were analyzed for detection of C trachomatis. When results differed between tests, specimens were evaluated by direct immunofluorescence staining. RESULTS: The prevalence of chlamydial infection was 2.4%. The characteristics of patients positive for Chlamydia were: average age, 24 years; first sexual encounter at age 21 years, one partner and six to nine months of gestation. The sensitivity, specificity, accuracy, positive predictive values and negative predictive values were 100%, 99.18%, 99.20%, 75% and 100%, respectively, for Papanicolaou staining; 100%, 92.62%, 92%, 25% and 100% for EIA; and 100%, 100%, 100% and 100% for PCR. CONCLUSION: Both Papanicolaou staining and PCR were adequate for diagnosis of C trachomatis infection. EIA was not reliable and therefore is not recommended for use as a diagnostic technique in a pregnant population with low risk and low prevalence.     

Evaluation of two fluorescent test kits for detection of selectedBacteroides species in clinical specimens

Two pools of isothiocyanate fluorescein-conjugated rabbit antisera toBacteroides fragilis, B. thetaiotaomicron, B. vulgatus, B. distasonis, B. ovatus, and toB. melaninogenicus, subsp.melaninogenicus andintermedius, andB. asaccharolyticus, respectively, were used in immunofluorescent (IF) tests of smears of 122 clinical specimens from a variety of sources, including abscesses and wounds. Smears of broth medium of 14 blood cultures were also tested. Bacteria of the species and subspecies mentioned were detected by the IF tests in 100 and by culture studies in 106 of the 136 speciments tested. Results of the culture studies indicated that 6 tests were false-negative by the IF test, while no false-positive tests were found. The sensitivities of the two test kits were 97% and 85%, respectively, while their specificities were 100%. The predicted value for a positive test with any of the two pools of antisera was 100%, while the predicted value for a negative test was 93% and 97%, respectively. The use of the two test kits (Fluoretec F and M) was found to be a valuable means for a rapid diagnosis of human infections with theBacteroides species mentioned.     

Diagnosis of Streptococcus pneumoniae meningitis by polymerase chain reaction amplification of the gene for pneumolysin

Diagnosis of bacterial meningitis has long been based on classical methods of Gram stain, serological tests, and culture of cerebrospinal fluid (CSF). The performance of these methods, especially culture and direct smear is thwarted by failure to detect bacteria following administration of antimicrobial agents and reluctance to performance lumbar punctures at admission. Indeed, patients with meningitis frequently receive antibiotics orally or by injection before the diagnosis is suspected or established Thus an alternative method has become necessary to help clinicians and epidemiologists to management and control of bacterial meningitis. We evaluate the application of a polymerase chain reaction-based (PCR) assay for amplification of pneumolysin gene (ply) to diagnosis of Streptococcus pneumoniae meningitis. The PCR assay sensitivity for CSF was 96% (95% confidence interval, CI, 90-99%) compared to a sensitivity of 59% for culture (95% CI 49-69%), 66% for Gram stain (95% CI 56-74%), and 78% for latex agglutination test (95% CI 69-86%); PCR specificity was 100% (95% CI 83-100%). PCR results were available within 4 h of the start of the assay. This molecular approach proved to be reliable and useful to identify this bacterium compared with other classical laboratory methods for identification of bacterial meningitis pathogens.     

Evaluation of an indirect serum ELISA and a bacteriological faecal culture test for diagnosis of Salmonella serotype Dublin in cattle using latent class models

AIMS: To evaluate a conventional bacteriological test based on faecal culture and an indirect serum ELISA for detection of S. Dublin infected cattle. To compare the predictive values of the two tests in relation to the prevalence. METHODS AND RESULTS: A total of 4531 paired samples from cattle in 29 dairy herds were analysed for presence of S. Dublin bacteria in faeces and immunoglobulins directed against S. Dublin lipopolysaccharide in an indirect serum ELISA. Sensitivity and specificity were estimated at two ELISA cut-off values using a validation method based on latent class models, which presumably provides less biased results than traditional validation methods. Stratification of data into three age groups gave significantly better estimates of test performance of the ELISA. Receiver operating characteristic (ROC) curves were constructed for comparison of overall performance of the ELISA between the three age groups. The sensitivity of the faecal culture test was low (6-14%). ELISA appeared to have a higher validity for animals aged 100-299 days of age than older or younger animals. Overall, the negative predictive value of the ELISA was 2-10 times higher than for the faecal culture test at realistic prevalence of infection in the test population. CONCLUSIONS: The diagnostic sensitivity of the faecal culture test for detection of S. Dublin is poor, the specificity is 1. The superior sensitivity and negative predictive value of the serum ELISA makes this test preferable to faecal culture as an initial screening test and for certification of herds not infected with S. Dublin. SIGNIFICANCE AND IMPACT OF THE STUDY: A quantitative estimate of the sensitivity of a faecal culture test for S. Dublin in a general population was provided. ELISA was shown to be an appropriate alternative diagnostic test. Preferably, samples from animals aged 100-299 days of age should be used as these give the best overall performance of the ELISA. Plots of ROC curves and predictive values in relation to prevalence facilitates optimisation of the ELISA cut-off value.