The Impact of Borderline Quantiferon-TB Gold Plus Results for Latent Tuberculosis Screening under Routine Conditions in a Low-Endemicity Setting.

Quantiferon-TB Gold Plus (QFT-Plus) is an interferon gamma release assay used to diagnose latent tuberculosis (LTB). A borderline range (0.20 to 0.99 IU/ml) around the cutoff (0.35 IU/ml) has been suggested for the earlier QFT version. Our aims were to evaluate the borderline range for QFT-Plus and the contribution of the new TB2 antigen tube. QFT-Plus results were collected from clinical laboratories in Sweden and linked to incident active TB within 3 to 24 months using the national TB registry. Among QFT-Plus results from 58,539 patients, 83% were negative (<0.20 IU/ml), 2.4% were borderline negative (0.20 to 0.34 IU/ml), 3.4% were borderline positive (0.35 to 0.99 IU/ml), 9.6% were positive (≥1.0 IU/ml), and 1.6% were indeterminate. Follow-up tests after initial borderline results were negative (<0.20 IU/ml) in 38.3%, without any cases of incident active TB within 2 years. Applying the 0.35-IU/ml cutoff, 1.5% of TB1 and TB2 results were discrepant, of which 52% were within the borderline range. A TB2 result of ≥0.35 IU/ml with a TB1 result of <0.20 IU/ml was found in 0.4% (231/58,539) of all included baseline QFT-Plus test results, including 1.8% (1/55) of incident TB cases. A borderline range for QFT-Plus is clinically useful as more than one-third of those with borderline results are convincingly negative upon retesting, without developing incident active TB. The TB2 tube contribution to LTB diagnosis appears limited.

Performance of Uricult Trio assessed by a comparison method and external control panels in primary healthcare.

Using the comparison method, we have evaluated the technical performance of Uricult Trio by culturing on Uricult Trio and agar plates. Urine samples (477) from patients in primary healthcare were cultured in parallel in a microbiology laboratory. The result for Uricult Trio evaluated using the comparison method was incorrect in 32% of the cultures. We also studied the performance of Uricult Trio when used in primary healthcare by using external control panels. External control panels consisting of Uricult Trio, inoculated with known concentrations of certain bacterial strains, were used to assess the performance of Uricult Trio in primary healthcare during the period 1993-7. Aberrations in reports of concentration have ranged from 10% to 33%, failure in reporting of mixed culture from 0% to 91% and reporting of E. coli from 15% to 86%. There has been no sign of improvement over the years. The results indicate that Uricult Trio is unsuitable for indications other than exclusion of urinary tract infection or diagnosis of urinary tract infection caused by E. coli. Further, there is need for quality assurance and training activities at primary healthcare laboratories, probably best carried out in collaboration with local clinical microbiology laboratories.

Evaluation of two methods for improving quality of diagnosis of bacteriuria by culture in primary healthcare.

This study evaluates the effect of training on the results from Uricult Trio and an established urine culture when used at primary healthcare laboratories in two Swedish counties, Uppsala and Värmland. Urine cultures and dipslides, Uricult Trio, performed at these laboratories were interpreted a second time at central laboratories. Interpretation errors at the primary healthcare laboratories were calculated. Primary healthcare laboratories also received external control panels with urine cultures and dipslides. There was one study period each year for 3 years in Uppsala and for 2 years in Värmland. A training programme was completed between study periods in Värmland. In Uppsala, primary healthcare laboratory results could be reviewed, as interpretations by the central laboratory were returned to them. The main outcome measures were the percentage of interpretation errors which, in the first study period, was 33-39%. This dropped to 15-19% in the second study period. In the results from the external control panels there were no striking differences between the studied areas and Sweden as a whole, except that Uppsala showed a better result in reporting E. coli and failed in 10% compared to Sweden 46%. A method for both quality assessment and education is to ask the primary healthcare laboratories to send cultures to the central laboratory for interpretation requesting their return to the primary healthcare laboratory with the interpretation from the central laboratory attached.

Detection of Helicobacter pylori antibodies in a pediatric population: comparison of three commercially available serological tests and one in-house enzyme immunoassay.

A serum immunoglobulin G enzyme immunoassay (EIA) for Helicobacter pylori antibodies already in use in adults was evaluated with 99 pediatric serum samples to determine its usefulness for the study of H. pylori disease in children. The reference method used was either the (13)C-urea breath test or a biopsy culture of gastric mucosa. In children, an EIA cutoff of 0.35 absorbancy unit yielded sensitivity, specificity, and positive and negative predictive values of 93, 97, 93, and 97%, respectively. The cutoff recommended when this EIA was published for use in adults was 0.70 absorbancy unit (H. Gnarpe, P. Unge, C. Blomqvist, and S. Mäkitalo, APMIS 96:128-132, 1988). Another subset of 169 serum samples taken from children was analyzed by four serological tests in order to compare the performance of the in-house EIA with the Pyloriset, HM-CAP, and Helico-G kits. For the 169 samples, 10 (5.9%) false-positives and no false-negatives occurred with the Helico-G, 3 (1.8%) false-positives and no false-negatives occurred with the Pyloriset, and 3 (1.8%) false-positives and 1 (0.6%) false-negative occurred with the HM-CAP. For the 169 samples, 1 (0.6%) false-positive and no false-negatives occurred with the in-house EIA. Serological detection of H. pylori antibodies with our EIA seems to be valuable in diagnosing H. pylori infection in children, but only if a lowered, specific pediatric cutoff is established. The commercial kits, particularly the Helico-G, seem to overdiagnose pediatric H. pylori infection. A positive serological test for H. pylori infection, particularly for children, needs to be confirmed by a reference method because of the possibility of spontaneous eradication of infection, with a lingering serological response.

Helicobacter pylori, active chronic antral gastritis, and gastrointestinal symptoms in alcoholics.

The frequency of Helocobacter pylori (Hp.) infection and active chronic antral gastritis among people with excessive alcohol consumption is not known. A high alcohol intake regularly causes acute gastroduodenitis. In this study, the prevalence of Hp. infection and active chronic antral gastritis in alcoholics compared with nonalcoholic controls was studied. Further, the frequency of gastrointestinal symptoms was registered. Diagnostic methods for Hp. were compared. Twenty-four alcoholics admitted to the hospital for detoxification underwent upper gastrointestinal endoscopy regardless of symptoms. Twelve individuals admitted to upper endoscopy mainly for dyspepsia, with low alcohol consumption and without gross pathology by upper endoscopy, were chosen as controls. Three diagnostic methods for Hp. were used: culture, direct microscopy, and histology. Hp. infection was found in 7 of the 24 alcoholics (29%) according to culture. In controls, 4 of 12 (33%) had a positive Hp. culture. In the alcoholic group, culture was more sensitive than histology. There was a good correlation between the different diagnostic methods in the control group. Histologically active chronic antral gastritis was found in 6 of the alcoholics (25%) and in 5 of the controls (42%). Five of the 7 Hp.-positive alcoholics and all of the Hp.-positive controls had an active chronic antral gastritis. Hp. infection is not more frequent in alcoholics than in controls. In both groups, there was a good correlation between Hp. infection and histologically, active chronic antral gastritis.