Significance and value of the Widal test in the diagnosis of typhoid fever in an endemic area.

The diagnostic value of the Widal test was assessed in an endemic area. The test was done on 300 normal individuals, 297 non-typhoidal fevers and 275 bacteriologically proven cases of typhoid. Of 300 normal individuals, 2% had an H agglutinin titre of 1/160 and 5% had an O agglutinin titre of 1/160. On the basis of these criteria a significant H and/or O agglutinin titre of 1/320 or more was observed in 93-97% of typhoid cases and in only 3% of patients with non-typhoidal fever. Of the sera from typhoid cases which gave a significant Widal reaction, the majority (79.9%) showed increases in both H and O agglutinins and 51 of 234 (21.8%) of these sera were collected in the first week of illness. The significance and implications of these findings are discussed.     

Widal test in diagnosis of typhoid fever in Turkey

We studied the value of the Widal tube agglutination test for the diagnosis of typhoid fever. The subjects were all adults >18 years of age and were divided into four groups: (i) 317 healthy blood donor controls, (ii) 31 bacteriologically confirmed patients with Salmonella enterica serotype Typhi, (iii) 21 patients with a clinical diagnosis of typhoid fever, and (iv) 41 febrile nontyphoid patients. Blood donor controls were screened with a slide agglutination test for the Salmonella enterica serotype Typhi O and H antigens, and positives were then tested with the Widal test. Acute- and convalescent-phase sera from patients in groups 2, 3, and 4 were obtained 7 to 10 days apart and tested by the Widal test. Using a cutoff of >or = 1/200 for the O antigen test performed on acute-phase serum gave a sensitivity of 52% and a specificity of 88% with a positive predictive value (PPV) of 76% and a negative predictive value (NPV) of 71%. This increased to 90% sensitivity and specificity with a PPV of 88% and an NPV of 93% when the convalescent-phase serum was tested. We concluded that O and H agglutinin titers of > or = 1/200 are of diagnostic significance. The Widal test is easy, inexpensive, and relatively noninvasive. It can be of diagnostic value when blood cultures are not available or practical. The results must be interpreted cautiously because of the low sensitivity of the test. The Widal test done on convalescent-phase serum gave more-reliable results with higher specificity and sensitivity.     

Comparison of the Vi indirect fluorescent antibody test with the Widal agglutination method in the serodiagnosis of typhoid fever.

The indirect fluorescent antibody test using a whole Salmonella typhi Vi suspension as the antigen has been evaluated for the diagnosis of typhoid fever. Results using sera from 140 patients with S typhi infections proved on culture show the test to have good sensitivity. The test appears to be highly specific, although it has not yet been investigated with respect to typhoid vaccination or in the context of infections due to salmonellas other than S typhi.     

Evaluation of passive bacterial agglutination for the diagnosis of typhoid fever.

We evaluated the reliability of a passive bacterial agglutination test to detect Salmonella typhi somatic antigen(s) in the sera of patients with typhoid fever. It was positive in 32 of 33 bacteriologically proven typhoid fever cases. Among 13 patients with a presumptive diagnosis of typhoid fever, 11 were positive by passive bacterial agglutination. The serum of one patient with paratyphoid A was also positive. Among 50 febrile patients without typhoid fever, one was persistently positive during the course of illness; 49 were negative. The sensitivity, specificity, and accuracy indices of the passive bacterial agglutination test were over 95%. The positive and negative predictive values were 94 and 98%, respectively.     

Comparison of serological test kits for diagnosis of typhoid fever in the Philippines

We evaluated four recent antibody-detection kits for typhoid fever by using 177 febrile patients from our hospital, in 75 of whom Salmonella enterica serotype Typhi grew. TUBEX performed best, achieving 94.7% sensitivity and 80.4% specificity. Typhidot, SD Bioline Typhoid, and Mega Salmonella were less specific and, in most cases, less sensitive.     

Comparison of methods for the diagnosis of typhoid fever.

Over five years the Bactec radiometric blood culture method yielded Salmonella typhi in 41 of 45 confirmed cases of typhoid fever, 90% of which were from the first culture set taken. Blood clot culture was positive in 18 (41%) of 44 confirmed cases and stool culture in 24 (59%) of 41. The yield from 2189 Widal clot cultures was only 0.03%. There were 68 positive results in 2258 unpaired Widal tests: 23 of them were falsely positive and 13 falsely negative, but in 11 out of 68 cases the Widal was the only positive laboratory test. It is concluded that routine clot culture is not cost effective if a sensitive blood culture method is used, and that the Widal test is useful only in selected patients.     

Immunoenzymatic dot-blot test for the diagnosis of enteric fever caused by Salmonella typhi in an endemic area

Objective: To develop a quick, solid-phase immunoenzymatic test, dot blot, to diagnose typhoid fever by the detection of IgG and IgM antibodies against three Salmonella typh antigens (lipopolysaccharide, crude and flagellar) and to compare the dot-blot test with an enzyme-linked immunosorbent assay (ELISA) using the same antigens and with the Widal agglutination test.
Methods: Blood culture was used as the definitive test. All tests were used for the study of the sera from three groups of individuals: 33 patients suffering typhoid fever, diagnosed by isolation of S. typhi in blood culture; 35 patients with other enterobacterial infections documented by culture; and 156 asymptomatic volunteers, all residents of the same endemic region (Urabá, Colombia).
Results: The best diagnostic efficiency was obtained by detecting IgG against a flagellar antigen dot blot, giving a sensitivity and specificity of 88%. Widal and ELISA tests showed lower diagnostic efficiencies.
Conclusions: The dot-blot test may be useful to diagnose typhoid fever in rural areas lacking technological resources with which to carry out blood cultures or ELlSA tests. The visual reading makes this test practical and cheap for these regions.     

Detection of Salmonella typhi protein antigen in serum and urine: a value for diagnosis of typhoid fever in an endemic area

Using haemoculture as the gold standard, a double antibody sandwich ELISA for the detection of Salmonella typhi Barber protein antigen (BP) was compared with the Widal test. Specimens used were serum and urine obtained from normal healthy individuals and from patients with typhoid fever, paratyphoid fever, pyrexia caused by other bacteria and pyrexia with negative haemoculture. The ELISA for antigenuria gave a significantly higher sensitivity, specificity, accuracy and positive predictive value than the Widal test (p less than 0.05). The ELISA for antigenaemia gave a significantly higher sensitivity and positive predictive value only. All other values were not significantly different. The timing of specimen collection was critical for sensitivity in the ELISA for antigenaemia and antigenuria, and the best results could be obtained by carrying out both assays simultaneously. The clearance of BP from serum into urine occurred around 16 days after the onset of fever in one patient. In two patients, BP could be detected in sera up to 3 weeks after the onset of fever. In two patients, serum BP could still be detected although haemoculture was negative.     

Serology of typhoid fever in an area of endemicity and its relevance to diagnosis

Currently, the laboratory diagnosis of typhoid fever is dependent upon either the isolation of Salmonella enterica subsp. enterica serotype Typhi from a clinical sample or the detection of raised titers of agglutinating serum antibodies against the lipopolysaccharide (LPS) (O) or flagellum (H) antigens of serotype Typhi (the Widal test). In this study, the serum antibody responses to the LPS and flagellum antigens of serotype Typhi were investigated with individuals from a region of Vietnam in which typhoid is endemic, and their usefulness for the diagnosis of typhoid fever was evaluated. The antibody responses to both antigens were highly variable among individuals infected with serotype Typhi, and elevated antibody titers were also detected in a high proportion of serum samples from healthy subjects from the community. In-house enzyme-linked immunosorbent assays (ELISAs) for the detection of specific classes of anti-LPS and antiflagellum antibodies were compared with other serologically based tests for the diagnosis of typhoid fever (Widal TO and TH, anti-serotype Typhi immunoglobulin M [IgM] dipstick, and IDeaL TUBEX). At a specificity of > or =0.93, the sensitivities of the different tests were 0.75, 0.55, and 0.52 for the anti-LPS IgM, IgG, and IgA ELISAs, respectively; 0.28 for the antiflagellum IgG ELISA; 0.47 and 0.32 for the Widal TO and TH tests, respectively; and 0.77 for the anti-serotype Typhi IgM dipstick assay. The specificity of the IDeaL TUBEX was below 0.90 (sensitivity, 0.87; specificity, 0.76). The serological assays based on the detection of IgM antibodies against either serotype Typhi LPS (ELISA) or whole bacteria (dipstick) had a significantly higher sensitivity than the Widal TO test when used with a single acute-phase serum sample (P < or = 0.007). These tests could be of use for the diagnosis of typhoid fever in patients who have clinical typhoid fever but are culture negative or in regions where bacterial culturing facilities are not available.     

A reverse passive latex agglutination test for the diagnosis of systemic candidosis

A new reverse passive latex agglutination test for the detection of serum antigen in systemic Candida albicans infection is reported. 1700 sera were examined from 91 patients who had either proven or suspected systemic candidosis, 183 patients who were colonized and 636 patients with no evidence of candidal infection. Thirty of the systemically infected patients had lymphoproliferative disorders and the rest a variety of surgical or medical diseases with no underlying neutropenia. The latex particles were sensitised with an antiserum raised in rabbits against a pressate of Candida albicans. The degree of antigenaemia was proportional to the likelihood of invasive disease such that a diagnostic cut-off point of 1 in 8 produced a test for systemic candidosis with a sensitivity of 90% and specificity of 80.4% in patients with lymphoproliferative disorders. In the remaining medical and surgical patients a diagnostic cut-off point of 1 in 10 produced a test with a sensitivity of 96.7% and specificity of 98.8%. The patients with lymphoproliferative disorders tended to produce lower serum antigen levels. The sera were also assayed for antibody using latex particles sensitised with pressate.     

The rapid slide agglutination test in the diagnosis of typhoid fevers and typhus

Of 10,000 sera examined for infectious diseases by both the rapid slide agglutination and the tube agglutination tests, 128 were found positive for typhus fever and 257 for typhoid and paratyphoid infections. Of 84 of the last mentioned cases of typhoid and paratyphoid, which were confirmed by cultural examination, 45 (53·5%) were negative to the tube test, whereas only one (1·2%) was negative to the slide test. Taking the total of 385 cases in which the clinical picture was typical and either one of the two serological tests positive, the tube test was negative in 183 cases (47·2%) whereas the slide test was negative once only (0·3%).     

Evaluation of an indirect haemagglutination kit for the rapid serological diagnosis of Mycoplasma pneumoniae infections.

A recently introduced indirect haemagglutination kit for the detection of Mycoplasma pneumoniae antibodies is compared with the standard method complement fixation. It is concluded that the kit provides a rapid, simple, and moderately sensitive means of detecting antibodies and, in some cases, enables these to be detected in the early, acute stage of infection.     

Stable erythrocyte diagnostic preparation for passive haemagglutination test with herpes simplex virus antigen.

A method for the preparation of stable suspensions of erythrocytes sensitized with herpes simplex virus (HSV) antigen and for their use in the passive haemagglutination test (PHAT) was developed. Formolized sheep erythrocytes were treated with tannin and sensitized with HSV antigen prepared from infected chick embryo cell culture by ultrasonication and virus extraction with alkaline glycine buffer. Antibody titres determined in the PHAT were higher than titres of neutralizing antibody. The specificity of the results was checked by the passive haemagglutination-inhibition test (PHAIT). The sensitized erythrocytes retained their activity for 5 months (the observation period) and gave reproducible results. The availability of stable erythrocyte diagnostic preparations simplifies the detection of herpesvirus antibody and makes the method widely applicable.