Characterisation of Mycobacterium tuberculosis isolates lacking IS6110 in Viet Nam

SETTING

The molecular diagnosis of tuberculosis (TB) in Viet Nam is often based on the detection of insertion sequence (IS) 6110 in Mycobacterium tuberculosis. However, 8-11% of M. tuberculosis strains in South-East Asia do not contain this target and this undermines the validity of these molecular tests.

OBJECTIVE

We quantified the frequency of M. tuberculosis strains lacking IS6110 in rural Viet Nam and studied their epidemiological and clinical characteristics.

DESIGN

Consecutively diagnosed adult TB patients in rural Southern Viet Nam submitted two sputum samples for culture, IS6110 restriction fragment length polymorphism (RFLP) spoligotyping and 15-loci variable number tandem repeat typing. Polymerase chain reaction (PCR) was performed to confirm the absence of IS6110 elements in strains lacking IS6110 hybridisation in RFLP.

RESULTS

Among 2664 TB patient isolates examined, 109 (4.1%) had no IS6110 element. Compared to other strains, these no-copy strains were less often resistant to anti-tuberculosis drugs, particularly to streptomycin (adjusted OR 0.2, 95%CI 0.1-0.5), and showed significant geographic variation. No associations with TB history or demographic factors were found.

CONCLUSIONS

Strains without the IS6110 target pose a problem in Viet Nam as regards false-negative molecular TB diagnosis in PCR. Compared to other strains circulating in Viet Nam, no-copy strains are more susceptible to anti-tuberculosis drugs.

Rapid serological assays for leptospirosis are of limited value in southern Vietnam

Leptospirosis, although ubiquitous and potentially lethal, is often not diagnosed. The seroprevalence of anti-Leptospira antibodies and the utility of two rapid tests for the serodiagnosis of the disease were studied in Binh Thuan, an area in southern Vietnam with favourable conditions for Leptospira. In an initial survey, blood samples from 44 patients with undifferentiated fever and 83 healthy subjects were each examined for anti- Leptospira antibodies using three tests: an ELISA; a latex card-agglutination test (Dri Dot); and a lateral-flow assay (LeptoTek Lateral Flow). In the ELISA, samples from 35% of the healthy subjects and 40% of the febrile patients were found to have titres of anti- Leptospira IgM of at least 1:80. Only one of the 13 patients checked again, in ELISA, 3 weeks later, showed the marked increase in IgM titre that is indicative of acute leptospirosis. In the initial survey, although the positive results of the lateral-flow assay, applied to whole blood and serum, showed a good agreement with those of the ELISA (kappa = 0.743), the results of the lateral-flow assay were often indeterminate. The card-agglutination test was more specific. The overall agreement between the results of the rapid tests and those of the ELISA was generally poor. When the samples classified as 'indeterminate' in the lateral-flow assay were considered positive, the maximum kappa-value for this assay applied to whole blood was only 0.512. In conclusion, it appears that high seroprevalences of anti- Leptospira IgM and low incidences of acute leptospirosis limit the diagnostic value of the rapid tests that were investigated. The lateral-flow assay is not specific enough. The card-agglutination test is possibly better but, because of the low incidence, its sensitivity could not be evaluated adequately in the present study.

Suspected tuberculosis case detection and referral in private pharmacies in Viet Nam

SETTINGS

Private pharmacies in Hanoi, Viet Nam.

OBJECTIVES

To explore the response of health care providers (HCPs) in private pharmacies to suspected tuberculosis (TB) patients.

METHODS

A simulated patient method combined with an interview in 128 randomly selected private pharmacies and 10 private pharmacies near TB hospitals.

RESULTS

In the simulated patient method and interview, respectively 59 (46%) and 70 (55%) of HCPs referred the TB suspect to general health care. Only 11 (9%) referred the simulated patient to a TB care facility. Fifty-two (42%) of the HCPs identified suspected TB from a fictitious case described on paper; 34 (27%) were aware that free treatment was provided under the National Tuberculosis Programme (NTP). Knowledge about free NTP treatment predicted a higher rate of direct referrals to TB facilities (OR 5.80, 95%CI 1.88-19.62) and greater ability to identify suspected TB from a fictitious case on paper (OR 5.14, 95%CI 2.36-11.73). Pharmacies with Good Pharmacy Practice (GPP) certification were less likely to refer simulated patients to TB facilities than non-GPP pharmacies (OR 0.10, 95%CI ≤0.01-0.79).

CONCLUSIONS

Nearly half of HCPs in private pharmacies do not refer TB suspects, possibly contributing to delays in diagnosis and treatment. Knowledge about free NTP treatment predicted better performance of HCPs.

Yield of interview screening and chest X-ray abnormalities in a tuberculosis prevalence survey

BACKGROUND

Tuberculosis (TB) prevalence surveys generally rely on a combination of screening methods to identify suspects eligible for sputum culture.

OBJECTIVE

To assess the yield of screening methods applied in a recent prevalence survey in Viet Nam and estimate the proportion of TB cases missed due to incomplete participation.

METHODS

TB suspects were identified based on self-reported TB history or productive cough by interview and chest X-ray (CXR). We calculated the case yield of these two screening methods by dividing the number of cases detected per method by the total number of cases detected. As not all participants underwent the full screening procedure, we recalculated the maximum yield of the screening methods using multiple imputation methods.

RESULTS

The yield from screening by interview and CXR were respectively 38% and 91%. Adjusting for missing data by multiple imputation, we estimated that we missed 9.9% (95%CI 6.8-14.2) of expected TB cases.

CONCLUSION

In prevalence surveys, screening by pre-structured interview is insufficient, and should be supplemented with CXR to achieve sufficient identification of TB cases. The effect of incomplete participation in the full screening procedure may be substantial and should be adjusted for in the analysis.

Health-seeking behaviour among adults with prolonged cough in Vietnam

OBJECTIVE

To assess health-seeking behaviour among adults with prolonged cough in a population-based, nationally representative sample in Vietnam.

METHODS

Cross-sectional survey conducted from September 2006 to July 2007. All inhabitants aged ≥15 years were invited for screening for cough, history of tuberculosis (TB) treatment and chest X-ray (CXR) examination. TB suspects, defined as any survey participant with CXR abnormalities consistent with TB, or productive cough for more than 2 weeks or TB treatment either currently or in the preceding 2 years submitted sputum specimens for smear examination and culture and provided information on health-seeking behaviour in an in-depth interview.

RESULTS

Of 94 179 persons participating in the survey, 4.6% had prolonged productive cough. Forty-four percentage of those had sought health care and reported pharmacies (35%), commune health posts (29%), public hospitals (24%) and private physicians (10%) as first point of contact. Only 7% had undergone sputum smear examination. Of TB suspects with prolonged productive cough, 2.9% were diagnosed with TB; 10.2% of these reported smear and 21.9% reported X-ray examination when visiting a health care facility. The average patient delay was 4.1 weeks (95% CI: 3.9-4.4) among cough suspects and 4.0 weeks (95% CI: 3.1-4.9) among TB cases.

CONCLUSIONS

In this Vietnamese survey, nearly half of persons with cough for more than 2 weeks had visited a health care provider. The commonest first health facility contacted was the pharmacy. Sputum smears were rarely examined, except in the provincial TB hospital. Our findings highlight the need to improve diagnostic practices by retraining health staff on the performance of sputum examination for TB suspects.

Measurement of exhaled nitric oxide as a potential screening tool for pulmonary tuberculosis

BACKGROUND

There is a need for low-technology, inexpensive screening tools for active tuberculosis (TB) case finding.

OBJECTIVE

to assess the potential usefulness of measuring exhaled nitric oxide (eNO).

DESIGN

Cross-sectional comparison in Hanoi, Viet Nam, comparing 90 consecutive smear-positive, culture-confirmed TB patients presenting at a referral hospital with office workers (no X-ray confirming TB) at this hospital (n = 52) and at a construction firm (n = 84). eNO levels were analysed using a validated handheld analyser.

RESULTS

eNO levels among TB patients (median 15 parts per billion [ppb], interquartile range [IQR] 10-20) were equal to those among construction firm workers (15 ppb, IQR 12-19, P = 0.517) but higher than those among hospital workers (8.5 ppb, IQR 5-12.5, P < 0.001). Taking the hospital workers as the comparison group, best performance as a diagnostic tool was at a cut-off of 10 ppb, with sensitivity 78% (95%CI 68-86) and specificity 62% (95%CI 47-75). Test characteristics could be optimised to 84% vs. 67% by excluding individuals who had recently smoked or consumed alcohol.

CONCLUSION

While eNO measurement has limited value in the direct diagnosis of pulmonary TB, it may be worth developing and evaluating as a cost-effective replacement of chest X-ray in screening algorithms of pulmonary TB where X-ray is not available.

Operational research for improved tuberculosis control: the scope, the needs and the way forward

The promotion of research is one of the main components of the World Health Organizations Stop TB Strategy, which includes 'programme-based operational research (OR)' and 'research on introducing new tools into practice'. The importance of OR in improving tuberculosis (TB) control was recognised a long time ago, and historical OR studies have been instrumental in the development of major strategies for TB control. Although a growing number of OR projects are being conducted in the world today, little is known about their results or their likely impact on TB control programmes. As funding organisations increasingly recognise the need for OR, we propose a rational framework to conduct OR, which covers a spectrum from local setting-oriented to international policy guiding research, and determines the relevance, replicability and generalisability of the results. OR in TB control is aimed at 1) improving programme performance; 2) assessing the feasibility, effectiveness and impact of new strategies or interventions on TB control; and 3) collecting evidence to guide policy recommendations on specific interventions. This requires strengthened capacity to plan and conduct OR in low-income countries and appropriate support to conduct both nationally and internationally led OR projects. Suggestions are made for potential steps for improved purpose-driven OR, which may help to improve TB control locally and inform policy recommendations internationally.

Risk of travelling to the country of origin for tuberculosis among immigrants living in a low-incidence country

SETTING

Two thirds of tuberculosis (TB) patients in the Netherlands are foreign-born.

OBJECTIVE

To determine if travelling to the country of origin is a risk factor for TB among two different immigrant groups that have lived in the Netherlands for at least 2 years.

DESIGN

In this unmatched case-control study, the frequency and duration of travel to the country of origin in the preceding 12 months were compared between adult Moroccan and Turkish TB patients and community controls.

RESULTS

Moroccan patients had travelled more often (26/32 = 81%) in the preceding year than Moroccan controls (472/816 = 58%). The travel-associated odds ratio (OR) for TB among Moroccans was 3.2 (95%CI 1.3-7.7), and increased to 17.2 (95%CI 3.7-79) when the cumulative duration of travel exceeded 3 months. The corresponding population fraction of Moroccan TB cases attributable to recent travel was 56% (95%CI 19-71). Among Turkish immigrants TB was not associated with travel (OR 0.9, 95%CI 0.3-2.4).

CONCLUSION

Travel to the country of origin was a risk factor for TB among Moroccans, but not among Turkish people living in the Netherlands. The difference in travel-associated OR between these two immigrant groups is probably related to differences in TB incidence in these countries.

Household expenditure and tuberculosis prevalence in VietNam: prediction by a set of household indicators

OBJECTIVE

To study the association between TB and household expenditure in a nationwide TB prevalence survey in Viet Nam using nine household characteristics.

METHOD

To assess the prevalence of TB in Viet Nam, a nationwide stratified cluster sample survey was conducted from 2006 to 2007. Nine household characteristics used in the second Viet Nam Living Standards Survey (VLSS) were scored per household. In the VLSS dataset, we regressed these nine characteristics against household expenditure per capita, and used the coefficients to predict household expenditure level (in quintiles) in our survey and assess its relation with TB prevalence.

RESULTS

The prevalence of bacteriologically confirmed TB was 307 per 100,000 population in persons aged ≥ 15 years (95%CI 249-366). After adjustment for confounders, prevalence was found to be associated with household expenditure level: the rate was 2.5 times higher for those in the lowest household expenditure quintile (95%CI 1.6-3.9) than those in the highest quintile.

CONCLUSION

With a set of nine household characteristics, we were able to predict household expenditure level fairly accurately. There was a significant association between TB prevalence rates and estimated household expenditure level, showing that TB is related to poverty in Viet Nam.

Decrease in risk of tuberculosis infection despite increase in tuberculosis among young adults in urban Vietnam

OBJECTIVE

To assess whether the increase in tuberculosis (TB) notification rates among young adults in Vietnam reflects increased transmission in the population at large.

METHOD

Trends of case notification rates of new smear-positive TB were calculated from routinely reported data of district TB units over the period 1996-2005. Results from repeated tuberculin surveys among children aged 6-9 years were obtained to calculate the trend in annual risk of TB infection (ARTI).

FINDINGS

From 1996 to 2006, notification rates in the age group 15-24 years increased by 4.3% per year, and more so in highly urbanised (6.7%) than in rural districts (1.7%). The ARTI in urban districts declined from 2.4% in 1992 to 1.2% in 1998 and 0.9% in 2005. In rural districts, the ARTI increased from 0.7% in 1991 to 1.2% in 1997, and then declined to 0.9% in 2006.

CONCLUSION

The increase in TB notification rates among young adults in Ho Chi Minh Province is accompanied by a decrease in ARTI in children. This suggests that the trend in TB notification among young adults reflects increased rates of progression from infection to disease and/or increased transmission within this age group, rather than increased transmission in the population at large.

Liquid culture for Mycobacterium tuberculosis: proceed, but with caution

Attempts to improve the diagnosis of tuberculosis (TB) in high-burden countries has resulted in significant funding and initiatives to change the method of diagnosis of TB from light microscopy supplemented with X-ray to a sophisticated diagnostic algorithm based on the latest technological innovations. Such activities are overdue and should be welcomed, but the lack of skills and support available to interpret and use the results represents a danger. The introduction of new diagnostic methods, particularly liquid culture, should be carefully structured according to the local situation, failing which frustration and the disruption of previously underdeveloped but adequately functioning laboratories may result.

Interferon-gamma release assays in immigrant contacts and effect of remote exposure to Mycobacterium tuberculosis

OBJECTIVE

To assess the association between remote exposure to tuberculosis (TB) and results of the tuberculin skin test (TST), and two interferon-gamma release assays (IGRAs)-QuantiFERON-TB Gold In-Tube (QFT-GIT) and T-SPOT.TB-in immigrant contacts of sputum smear-positive TB patients.

METHODS

Immigrants aged >or=16 years in close contact with smear-positive TB patients were included. QFT-GIT and T-SPOT.TB were performed if the TST induration size was >or=5 mm. Associations between test results and origin from an endemic country were assessed.

RESULTS

Of 433 close contacts, 322 (74%) had TST >or=5 mm, of whom, 282 (88%) had valid test results for all assays. Positive QFT-GIT results were obtained for 152/282 (54%) and positive T-SPOT.TB for 168/282 (60%). After adjustment for age, sex and recent contact, positive IGRA results and TST results >/=10 mm were found to be more frequent among immigrants who originated from Africa, in particular sub-Saharan Africa.

CONCLUSION

When IGRAs are used to determine latent TB infection in foreign-born individuals, positive findings not only relate to recent TB infection, but also reflect prior TB exposure in the country of origin. This late reactivity will limit their usefulness in contact investigations among immigrants originating from endemic areas.

[HIV-test policy for tuberculosis patients in the Netherlands]

OBJECTIVE

To compare the proportion of tuberculosis patients tested for HIV infection, before and after introduction of highly active antiretroviral therapy (HAART) in the Netherlands, and to analyse predictive factors for performing an HTV-test in this population.

DESIGN

Retrospective.

METHOD

Whether patients had been tested for HIV, was investigated in random samples consisting of 200 patients, who were registered in the Netherlands Tuberculosis Register (NTR) in the years 1995 and 2001 respectively.

RESULTS

The number of patients tested for HIV was 29 out of 84 (16%) in 1995, and 39 out of 190 (21%) in 2001 (not significant). HIV-tests had been carried out most frequently among homeless patients (71%), drug addicts (56%) and alcohol-abusing patients (60%). Significant predictive factors for HIV testing were place of residence (city), localisation of disease (pulmonary tuberculosis in combination with extrapulmonary tuberculosis) and place of origin (sub-Saharan Africa).

CONCLUSION

Despite introduction of HAART during this period, in the Netherlands the proportion of tuberculosis patients tested for HIV did not significantly increase between 1995 and 2001. HIV testing was mainly limited to tuberculosis patients from risk groups.

Low tuberculosis notification in mountainous Vietnam is not due to low case detection: a cross-sectional survey

BACKGROUND

Studies show that tuberculosis notification declines with increasing altitude. This can be due to declining incidence or declining case detection. In Vietnam notification rates of new smear-positive tuberculosis in the central mountainous provinces (26/100,000 population) are considerably lower than in Vietnam in general (69/100,000 population). In order to clarify whether this is explained by low incidence or low case detection, we aimed to assess the prevalence of new smear-positive tuberculosis among adults with prolonged cough in three mountainous provinces in central Vietnam.

METHODS

A house-to-house survey of persons (> or = 15 years) was carried out in twelve randomly selected districts in 2003. Three sputum specimens were microscopically examined of persons reporting a prolonged cough (> or = 3 weeks). Case detection was assessed by the ratio between notification and prevalence.

RESULTS

Of 68,946 included persons (95% response), 1,298 (1.9% 95%CI 1.8-2.2) reported a prolonged cough. Of these, eighteen were sputum smear-positive of whom two had had anti-tuberculosis treatment. The prevalence of new smear-positive tuberculosis was 27/100,000 (95%CI 11-44/100,000) and the notification rate was 44/100,000 among persons > or = 15 years. The estimated case detection rate was 76%.

CONCLUSION

Low tuberculosis notification in this mountainous setting is probably a true reflection of low tuberculosis incidence. Possible causes for low incidence in mountainous areas include low transmission rates or altitude-related differences in pathology.

HIV-related mortality among tuberculosis patients in The Netherlands, 1993-2001

Human immunodeficiency virus (HIV) infection in tuberculosis (TB) patients in The Netherlands during the period 1993-2001 was associated with an increased risk of death (adjusted odds ratio 4.71, P < 0.002). Age and sex-standardised mortality rates among HIV-infected TB patients decreased significantly over time, from 22.9% in 1993-1995 to 11.8% in 1999-2001 (P < 0.001). No such change was observed for HIV-negative patients. The decrease in mortality is likely due to the more widespread use of highly active antiretroviral therapy (HAART).

Steep increases in tuberculosis notification among young men in the industrialised districts of Danang, Vietnam

BACKGROUND

Tuberculosis (TB) notification is increasing among young adults in urban provinces in Vietnam, despite having achieved World Health Organization targets for treatment success and case detection.

OBJECTIVES

To identify causes for non-declining TB case rates in an urban area of Vietnam, and to describe trends in new smear-positive pulmonary TB notification by age, sex and district in the period 1999-2004 in Danang City, Vietnam.

RESULTS

Age and sex-standardised notification rates declined by 1.3% (95%CI -2.3-0.3%) annually. Notification rates among men aged 15-44 in Danang City increased significantly (5%, 95%CI 2.4-7.7 annually), most notably in industrialised districts (>or=12% annually).

CONCLUSION

TB notification rates among young men in an urban setting in Vietnam increased most notably in industrialised districts. We hypothesise that this is due to poor living and working conditions and internal migration rather than to an emerging human immunodeficiency virus epidemic.

HIV prevalence among tuberculosis patients in The Netherlands, 1993-2001: trends and risk factors

OBJECTIVES

To describe the prevalence and predictive factors of human immunodeficiency virus (HIV) infection among tuberculosis (TB) patients in The Netherlands during the period 1993-2001.

DESIGN

Data were obtained from the national surveillance register of all patients notified with TB (all forms) during the period of the study. In addition, records or discharge notes were checked of a random sample of 200 TB patients notified in 1995 and another 200 in 2001.

RESULTS

Of 13 269 patients diagnosed with TB, 542 were HIV-positive (4.1%). Prevalence was 4.1% in 1993-1995, 3.8% in 1996-1998 and 4.4% in 1999-2001. The highest prevalence was observed among drug users (29.2%), homeless patients (20.1%) and patients residing illegally in the country (9.1%). Compared with the period 1993-1995, the relative risk of HIV infection in the periods 1996-1998 and 1999-2001 decreased significantly for drug using patients (P = 0.006), and increased for patients from African countries (P < 0.001). According to patient records, 29/184 (16%) had been tested for HIV in 1995 and 39/190 (21%) in 2001 (P = 0.289); 18 patients tested positive (4.8%).

CONCLUSION

Although the prevalence of HIV among TB patients in The Netherlands remained stable between 1993 and 2001, the distribution of risk groups changed over this period.

Drug resistance among smear-positive tuberculosis patients in Ho Chi Minh City, Vietnam

OBJECTIVES

To assess the pattern of drug resistance among smear-positive tuberculosis (TB) patients in an inner city area in Vietnam.

METHODS

A random sample of patients diagnosed by the national TB programme (NTP) were offered HIV testing and submitted sputum for Mycobacterium tuberculosis drug sensitivity testing.

RESULTS

Of 1433 isolates from new patients, 360 (25%) were resistant to isoniazid (INH), 57 (4.0%) to rifampicin (RMP), 421 (29%) to streptomycin (SM) and 28 (2.0%) to ethambutol. Among 401 previously treated patients, this was 218 (54%), 109 (27%), 217 (54%) and 26 (7%), respectively. Multidrug resistance (MDR) was observed in 55 (3.8%) new and 102 (25%) previously treated patients. RMP resistance was strongly associated with resistance to INH (OR 46) and INH plus SM (OR 91, P = 0.004). Prevalence of drug resistance tended to decrease with age. Neither any resistance nor MDR was significantly associated with HIV infection.

CONCLUSIONS

In this inner city area, levels of drug resistance, in particular of MDR among previously treated patients, are high. This may be related to the use of NTP regimens in the context of highly prevalent combined SM and INH resistance which may favour acquisition of RMP resistance.

Treatment outcomes by drug resistance and HIV status among tuberculosis patients in Ho Chi Minh City, Vietnam

OBJECTIVE

To assess the combined effects of drug resistance, HIV infection and treatment regimen on treatment outcomes of smear-positive tuberculosis patients in Ho Chi Minh City, Vietnam.

METHODS

A representative sample of patients diagnosed in 1998-2000 in 12 urban districts was offered HIV testing and submitted sputum for Mycobacterium tuberculosis culture and drug susceptibility testing. New patients were treated with 2SHRZ/6HE in nine districts and with 2SHRZ/4RH in three districts.

RESULTS

The cure rate was 87% (1240/1430) among new patients compared to only 73% (287/391) among previously treated patients. Failure was associated with multidrug resistance (adjusted odds ratios [aOR] 49.6 and 16.6, respectively) and combined resistance to isoniazid (INH) and streptomycin (SM) (aOR 13.4 and 4.8), but not with HIV infection. New patients had an increased risk of failure on treatment with 2SHRZ/4RH compared to 2SHRZ/6HE if the isolate was resistant to INH and SM (aOR 2.8, P = 0.016). Death during treatment occurred in 15 of 50 HIV-infected patients (30%). Mortality was significantly associated with HIV infection (aOR 29.9), multidrug resistance (aOR 4.7) and other resistance to two or more drugs (aOR 2.1).

CONCLUSION

In Vietnam, adaptation of treatment regimens should be considered, and interventions are needed to reduce the high mortality among HIV-infected patients.

[Large-scale outbreak investigation for tuberculosis in Zeist]

Recently a large-scale outbreak investigation was held among customers of a supermarket in the Dutch town of Zeist after an employee was diagnosed with smear-positive pulmonary tuberculosis. About 14,000 people had a tuberculin skin test and an additional 6,000 had a chest X-ray. About 400 positive skin tests and 8 cases of active tuberculosis have been reported so far. Investigation of contacts of infectious tuberculosis cases is an important tool in tuberculosis control in low-prevalence countries. It includes chest X-ray examination for active pulmonary tuberculosis after or instead of tuberculin skin testing, and identifying contacts with latent tuberculosis infection followed by preventive treatment. Investigation of household and other close contacts is highly effective. This may not be true for sporadic contacts who are likely to have a low risk of infection, such as in this investigation, where the prevalence of recent infections estimated from reported data is only 3%. The benefits of detecting these cases must be weighed against the costs of such large-scale operations and the probability of false-positive skin test results.

Tuberculin skin test: estimation of positive and negative predictive values from routine data

OBJECTIVE

To estimate, using routinely available data, the predictive values of tuberculin testing with 2TU RT23 for detection of latent tuberculosis infection (LTBI) in the Dutch population as a basis for recommendations on cut-off values at various levels of infection prevalence.

DESIGN

Smoothed distributions of TST reactions among 312 tuberculosis patients and 2848 healthy non-BCG-vaccinated persons were used to estimate the sensitivity and specificity at various cut-off values.

RESULTS

Sensitivity was 98.9% at 5 mm, 95.4% at 10 mm and 79.8% at 15 mm cut-off. Specificity with the corresponding cut-offs was 95.3%, 96.3% and 97.1% before and 98.0%, 98.8% and 99.6% after adjustment for presumed LTBI. At 10 mm, the positive predictive value (PPV) was > 75% if the infection prevalence in the tested population was at least 10%, but strongly declined with lower prevalences. For lower prevalences a cut-off of 15 mm was proposed, as this results in a higher PPV without greatly affecting the negative predictive value.

CONCLUSION

Estimation of the predictive values of the TST from routine data can be useful for establishing cut-off values for detection of LTBI in different populations with different tuberculin preparations.

[Indications for, and the significance of, the tuberculin test in the Netherlands]

The almost 100-year-old tuberculin skin test still is the gold standard for diagnosing Mycobacterium tuberculosis infection. The sensitivity of this test with the usual cut-off values is high, but may be decreased with impaired cellular immunity and at older age. The specificity is primarily determined by cross-reactivity to atypical mycobacterial infections and vaccination with Bacillus Calmette-Guérin (BCG). Positivity of the skin test after BCG vaccination decreases with time after vaccination and depends on the age when vaccinated. The tuberculin reaction can be boosted by repeated tuberculin skin tests over a short time period, whereby the anamnestic immune response is stimulated. This boosting phenomenon occurs mostly with atypical mycobacterial infections, after BCG vaccination and at older age. Interpretation of the tuberculin skin test depends on the indication for the test, the expected risk of latent tuberculosis infection, higher prevalence of 'old' tuberculosis in elderly Dutch people and immigrants, BCG vaccination status and, if a baseline value is available, the boosting phenomenon. Its role in the diagnosis of tuberculosis is limited.

[Limited tuberculin screening participation amongst travellers to countries with high tuberculosis incidence; reason to consider BCG vaccination for some travellers]

OBJECTIVE

To determine the compliance amongst Dutch travellers to high tuberculosis-incidence countries with a screening procedure involving a tuberculin skin test before and after the trip.

DESIGN

Prospective study.

METHOD

Nine hundred and eighty-eight tuberculin-negative Dutch people who travelled to high tuberculosis-incidence countries for 3 to 12 months were studied for their compliance with an advised screening procedure of repeat tuberculin skin testing 2 to 4 months after return. At 2 of the 4 participating health services, data were also collected on extra calls made and the pertinent time investments.

RESULTS

Five hundred and ninety-nine travellers (61%) were compliant with the screening procedure. Of those for whom the data was available (n = 417), 33% (98/300) of the compliant travellers required extra calls. These took an average of 30 min per extra traveller tested as a result. Compliance varied according to health service and was better amongst travellers to Africa. In addition, non-compliance was independently associated with male sex, work being the main travel purpose, and an undecided duration of travel on departure.

CONCLUSIONS

Compliance of Dutch travellers with tuberculin skin-test screening is limited, particularly if no extra calls are issued. Bacillus Calmette-Guérin vaccination appears to be preferable for travellers with undecided travel duration and persons travelling for work on a frequent basis.

[The tuberculin skin test in the Netherlands: new policies for an old test; guideline from the Netherlands Tuberculosis Control Policy Committee]

The primary function of tuberculin skintesting is to demonstrate latent tuberculosis infection. The Netherlands Tuberculosis Control Policy Committee revised the guideline for the use and interpretation of the test because of new insights and changes of the epidemiological situation. Tuberculin testing should target persons who are likely to benefit from treatment of latent tuberculosis infection, such as contacts of tuberculosis-source cases, persons with increased occupational risk of tuberculosis exposure and persons with an increased risk of breaking down from infection to active disease as a result of depressed cellular immunity. The contribution of the tuberculin skintest to the diagnosis of active tuberculosis is limited. Different cut-off values for a positive test result are recommended in order to obtain optimum positive and negative predictive values in different target groups. In screening programmes, if the initial test result is 3-9 mm, follow-up tests are only indicated after exclusion of boosting by the initial two-step method. In contact investigations and persons with immune disorders, a history of Bacillus Calmette Guérin (BCG) vaccination should not longer be regarded a contraindication for tuberculin testing.