BCG vaccination and the prevalence of latent tuberculosis infection in an aboriginal population.

SETTING: Estimations of prevalence of latent tuberculous infection (LTBI) are confounded by factors known to influence the results of the tuberculin skin test (TST) such as age, contact history and bacille Calmette-Guerin (BCG) vaccination. Appropriate interpretation of TST results is necessary to ensure LTBI treatment for those at greatest risk. OBJECTIVE: To document the prevalence of LTBI in Aboriginal people living on a reserve in British Columbia (BC) and to determine the influence of BCG. DESIGN: A population-based, retrospective descriptive analysis of all epidemiological data collected for the on-reserve Aboriginal programme in BC (1951-1996). RESULTS: Of 17615 persons who received a TST during the study period, 42% had received BCG. During the study period, an average of 2517 TSTs were completed per year (SD = 1228) among persons with an average age of 26 years (SD = 16). Among all subjects, the average prevalence of LTBI was 25% (95 %CI 24-25). The presence of BCG (OR = 3.1, 95%CI 2.8-3.4) and multiple BCGs (OR = 10.2, 95%CI 7.7-13.6) were both associated with a positive TST. A positive TST was also associated with a shorter duration in years between the most recent BCG and the TST. CONCLUSION: The average prevalence of LTBI in a sequential sample of Aboriginal people living on a reserve in BC was estimated at 25%. BCG, especially in multiple doses, increased the likelihood of a positive TST.

Cataract surgical coverage and outcome in the Tibet Autonomous Region of China.

BACKGROUND: A recently published, population based survey of the Tibet Autonomous Region (TAR) of China reported on low vision, blindness, and blinding conditions. This paper presents detailed findings from that survey regarding cataract, including prevalence, cataract surgical coverage, surgical outcome, and barriers to use of services. METHODS: The Tibet Eye Care Assessment (TECA) was a prevalence survey of people from randomly selected households from three of the seven provinces of the TAR (Lhoka, Nakchu, and Lingzhr), representing its three main environmental regions. The survey, conducted in 1999 and 2000, assessed visual acuity, cause of vision loss, and eye care services. RESULTS: Among the 15,900 people enumerated, 12,644 were examined (79.6%). Cataract prevalence was 5.2% and 13.8%, for the total population, and those over age 50, respectively. Cataract surgical coverage (vision <6/60) for people age 50 and older (85-90% of cataract blind) was 56% overall, 70% for men and 47% for women. The most common barriers to use of cataract surgical services were distance and cost. In the 216 eyes with cataract surgery, 60% were aphakic and 40% were pseudophakic. Pseudophakic surgery left 19% of eyes blind (<6/60) and an additional 20% of eyes with poor vision (6/24-6/60). Aphakic surgery left 24% of eyes blind and an additional 21% of eyes with poor vision. Even though more women remained blind than men, 28% versus 18% respectively, the different was not statistically significant (p = 0.25). CONCLUSIONS: Cataract surgical coverage was remarkably high despite the difficulty of providing services to such an isolated and sparse population. Cataract surgical outcome was poor for both aphakic and pseudophakic surgery. Two main priorities are improving cataract surgical quality and cataract surgical coverage, particularly for women.

Blindness and eye diseases in Tibet: findings from a randomised, population based survey.

BACKGROUND: Public health officials of the Tibet Autonomous Region (TAR) of China requested a survey of blindness, eye diseases, and eye care service utilisation to assist the development of a 10 year blindness prevention and treatment plan. The objective of the survey was to determine the prevalence of blindness and visual impairment, as well as cataract surgical coverage and surgical outcome in the TAR. METHODS: The Tibet Eye Care Assessment was a cross sectional prevalence study of three of the seven prefectures (provinces) of the TAR (Lhoka, Nakchu, and Lingzhr) selected to represent its three main environmental regions. The survey sample was selected using a random multistage cluster method. Two teams conducted the survey in a standardised fashion in each prefecture, Lhoka during May and Nakchu during June 1999, and Lingzhr during May 2000. Visual acuity, cause of vision loss, trachoma, and vitamin A deficiency were included in the clinical examination. RESULTS: Among the 15,900 people enumerated, 12,644 were examined for an overall response rate of 79.6%. The crude prevalence of blindness (presenting better eye visual acuity of less than 6/60) was 2.3%; age and sex adjusted blindness prevalence was 1.4% (95% CI 1.3 to 1.5). Visual impairment (better eye presenting visual acuity of 6/24 to 6/60) was found in 10.9% (95% CI 10.5 to 11.2) of the population (age and sex adjusted). Cataract was the primary cause of blindness (50.7%), followed by macular degeneration (12.7%) and corneal opacity (9.7%). CONCLUSION: Blindness is a serious public health problem in Tibet, with prevalence higher than in similar studies in eastern China. As elsewhere in the world, women have an excess burden of blindness compared to men. About 75% of blindness in Tibet can be either prevented or treated. Eye care planning for Tibet must focus on cataract, particularly among women.

Changes in blindness prevalence over 16 years in Malawi: reduced prevalence but increased numbers of blind.

BACKGROUND/AIMS: In the coming two decades significant increases in the burden of blindness are anticipated unless concerted efforts are made to improve eye care in developing countries. Evidence of changing prevalence rates or numbers of blind people are few. The change in blindness prevalence and the number of blind people in an adult population of Malawi was measured over a 16 year period. METHODS: In 1999 a population based survey of blindness in adults (age 50+) was conducted in Chikwawa district of Malawi. Visual acuity and cause of vision loss were recorded for each eye independently. Blindness was defined as presenting better eye vision of <6/60. Findings from a 1983 survey of blindness in the same district (using similar methods) were re-analysed to be comparable with the survey conducted in 1999. RESULTS: Among 1630 enumerated adults 89% were examined. The age adjusted prevalence of blindness in the adult population was 5.4% and more common in women than men. In each age group the prevalence of blindness was lower in 1999 than in 1983; the overall reduction in blindness was 31%. During this period the 50+ population in Malawi increased almost twofold. Extrapolating the Chikwawa district data to the Malawi population reveals that the number of blind people has increased by 24%; the increase is primarily because of the large increase in the size of the most elderly group, aged 70 and above. CONCLUSION: The majority of blind people in Chikwawa (1983 and 1999) are in the age group 70 and over. This group has had the largest proportional increase in population size in this time. Services in this population have improved in the intervening 16 years and yet there was still an increase in the number of blind people. There was little change in excess blindness in women, suggesting that the same barriers that prevented utilisation of services in 1983 probably persist in 1999. Efforts to reach the most elderly and to reach women are needed to lead to a reduction in blind people in settings such as rural Malawi.

Prevalence and predictors of default from tuberculosis treatment in Hong Kong.

OBJECTIVE: To determine the prevalence and risk factors of default from tuberculosis treatment in Hong Kong. DESIGN: Retrospective study. SETTING: Data were obtained from programme forms completed by physicians in the Hong Kong Government Tuberculosis and Chest Service and from medical records from Hong Kong chest clinics. PATIENTS: In all, 5917 patients registered for antituberculous drug therapy in 1996; medical records of 5757 patients were reviewed. MAIN OUTCOME MEASURES: Patients who defaulted treatment were defined as those who had failed to collect medication for more than 2 consecutive months after the date of the last attendance during the course of treatment. Demographic and clinical characteristics, including history, treatment, and outcome, were compared between defaulters and non-defaulters, both among the whole group and among those with pulmonary disease. RESULTS: There were 442 (8%) patients who defaulted from treatment. Forty-five percent of those who defaulted did so in the first 2 months of treatment. Key risk factors associated with non-compliance were a history of default, male sex, and a history of concomitant liver disease or lung cancer. Among patients with pulmonary tuberculosis (381 defaulters and 1537 non-defaulters), multiple drug resistance was also associated with default from treatment. Among defaulters with pulmonary disease, 39% were still bacteriologically positive at the time of default. CONCLUSION: Default from treatment may be partially responsible for the persistent high rates of tuberculosis in Hong Kong in the past decade. Health professionals should ensure that all barriers to treatment be removed and that incentives be used to encourage treatment compliance.

Tuberculosis in Hong Kong-patient characteristics and treatment outcome.

OBJECTIVES: To identify the general characteristics of patients with tuberculosis, and to evaluate their treatment outcomes. DESIGN: Retrospective study. SETTING: Tuberculosis and Chest Service, Department of Health, Hong Kong. SUBJECTS AND METHODS: All patients with tuberculosis registered for treatment from 1 January 1996 to 31 December 1996 were included in the study. Information was extracted from their medical records at treatment commencement and at 12 and 24 months after treatment was instigated. Data gathered included demographic data, past treatment, site of disease, case category, treatment regimen, bacteriological status, and treatment outcome. RESULTS: There were 5757 patients for analysis. Approximately one third of patients were aged 60 years or older, and 69.1% were male. Pulmonary disease alone occurred in 77.7% of patients, while both pulmonary and extrapulmonary diseases occurred in 8.6%. New patients comprised 84.6% of cases, and 16.3% had concomitant illnesses. There was excess risk of disease among patients who were male, elderly, or who had silicosis. Only 0.1% of patients were co-infected with human immunodeficiency virus infection. Among the 5757 cases evaluated, 1324 (23.0%) were new patients with a positive sputum smear, 299 (5.2%) were patients who were retreated with a positive sputum smear, and 4134 (71.8%) were new or retreatment patients with a negative sputum smear. The overall treatment completion rates at 12 and 24 months were 80.4% and 84.8%, respectively. Males and patients aged 60 years or older had lower treatment completion rates. Non-adherence, transfer to other services, and mortality among the elderly were key factors influencing treatment outcomes. Co-morbidity was associated with better case-holding, and this more than compensated for its effect on prolongation of treatment and mortality. CONCLUSIONS: There was an excess risk of tuberculosis among male and elderly patients, who also had a less favourable outcome. Active screening of clearly identified risk groups may be appropriate but requires the completion of more in-depth studies and careful cost-effectiveness analyses. Further efforts with respect to case-holding are indicated to address treatment defaulting and transfer rates.

Extra-pulmonary and pulmonary tuberculosis in Hong Kong.

OBJECTIVE: To compare the characteristics of patients with pulmonary and extra-pulmonary tuberculosis and to describe the organ involvement, diagnosis and treatment of extra-pulmonary tuberculosis. MATERIALS AND METHODS: All patients with a diagnosis of tuberculosis treated by the Hong Kong Government Tuberculosis and Chest Service (Chest Service) in 1996 were studied. RESULTS: Of the 5757 patients treated, 13.7% had extra-pulmonary tuberculosis alone and 8.6% had both extra-pulmonary tuberculosis and pulmonary tuberculosis. Extra-pulmonary tuberculosis was more common in women under 30 and over 75 years of age. Only six patients had human immunodeficiency virus (HIV) infection, of whom two had extra-pulmonary tuberculosis. The most common site of extra-pulmonary involvement was the pleura, followed by the lymph nodes. Miliary tuberculosis occurred in only 2.9%. Lymph node involvement occurred significantly higher in women, while pleural disease was significantly higher in men. The duration of treatment varied according to the site of disease, being shorter (6 months) for those with pleural disease only and >9 months for those with miliary, meningeal, gastrointestinal and genitourinary disease; 80.3% completed treatment at 12 months and 85.5% at 24 months. Of those who completed treatment, 1.4% had a relapse of disease at 24 months follow-up; there was no significant difference between those with pulmonary or extra-pulmonary disease. CONCLUSION: In Hong Kong, extra-pulmonary tuberculosis is common, affecting 22.3% of TB patients, and is unrelated to HIV infection. There are sex differences in the organs most commonly affected. The rate of relapse of disease is low for those who completed treatment, irrespective of the site of involvement.

Tuberculosis in the elderly in Hong Kong.

BACKGROUND: The rate of tuberculosis in Hong Kong has declined dramatically since the 1950s, but has remained high during the past decade, at around 110/100,000. The reason for the persistent high rate is not clear. OBJECTIVES: To study the trend of tuberculosis in Hong Kong during the past decade (1989 to 1998) and the clinical characteristics of tuberculosis patients > or = 60 years of age, and compare them with those of the younger age groups. METHODS: Notification rates of tuberculosis from 1989 to 1998 were obtained from the Hong Kong Government Tuberculosis and Chest Service (Chest Service), Department of Health, Hong Kong. In addition, all patients registered at the Chest Service for treatment of tuberculosis in 1996 were studied. RESULTS: During the past decade, the notification rate of tuberculosis, which included both bacteriologically confirmed and clinically active but bacteriologically not confirmed cases, decreased in those under 60, remained unchanged in those between 60-69, and increased in those > or = 70 years of age. An increase in the rate of bacteriologically confirmed cases (sputum smear or culture positive for Mycobacterium tuberculosis) in the older age groups was observed during the same period. In 1989, 31.9% of tuberculosis cases were over the age of 60 years; this proportion increased to 45.4% in 1998. The increase in the number of cases in those > or = 60 years could almost account for the total increase in number of cases during the last decade. Patients in the older age groups had more advanced disease at the time of diagnosis, and a higher proportion had comorbid illnesses. They also had significantly higher mortality compared with the younger age groups. CONCLUSION: The increasing longevity of the population and the high rate of tuberculosis in the elderly are important factors contributing to the persistent high rate of tuberculosis in Hong Kong in the past decade.

Sex differences in tuberculosis in Hong Kong.

SETTING: The Hong Kong Tuberculosis and Chest Service, Department of Health, Hong Kong. OBJECTIVE: To examine sex differences in the rate and clinical manifestations of tuberculosis in Hong Kong. DESIGN: Notification rates of tuberculosis during the past five decades were obtained from the Hong Kong Tuberculosis and Chest Service, Department of Health, Hong Kong. In addition, all patients registered with the Chest Service for treatment of tuberculosis in 1996 were studied. RESULTS: The rate of tuberculosis during the past five decades was consistently higher in men than in women, irrespective of age group. The sex difference in rates was highest among those aged over 60 years. In 1996, a higher proportion of women had extra-pulmonary tuberculosis than men; the main site of involvement was the lymph nodes. More women completed treatment at 12 months and fewer women missed treatment appointments. A higher proportion of men had relapse pulmonary disease that was more extensive, a history of previous default from treatment and co-morbid illnesses. CONCLUSION: There are sex differences in the rates and clinical manifestations of tuberculosis in Hong Kong. Study of sex differences is essential for targeting prevention programmes at groups at higher risk.

Contact examination for tuberculosis in Hong Kong is useful.

SETTING: The tuberculosis programme of the Hong Kong Government Tuberculosis and Chest Service. OBJECTIVE: To determine the outcome of examination of household contacts in Hong Kong. DESIGN: A retrospective cohort study of all household contacts of 970 randomly selected index cases from a total of 5757 registered for treatment with the Chest Service. RESULTS: Of 2678 household contacts (three/index case) identified, 90% were examined; 41 active cases were found, at a rate of 1720/100000 (95%CI 1238-2329). The rate was highest among two extremes of age, 3604/100000 (95%CI 990-3615) in children < or = 5 years and 3347/100000 (95%CI 1456-6489) in those >60 years of age. Contacts of index cases whose sputum smear and culture were positive had the highest rate of disease, 2904/100000 (95%CI 1669-4673); but contacts with negative bacteriology also had a high rate of 1478/100000 (95%CI 678-2789). Active cases identified through contact tracing could be source cases rather than secondary cases. Eight per cent of children aged < or = 5 years had positive tuberculin reactions; as BCG vaccination is given to all newborns, with 99% coverage in Hong Kong in the past 30 years, it was difficult to estimate the rate of infection in these children. CONCLUSION: In Hong Kong, an area with an intermediate burden of tuberculosis, contact investigation is a very useful procedure for active case finding.

Tuberculosis among aboriginal and nonaboriginal persons in British Columbia.

OBJECTIVE: To compare cases of tuberculosis (TB) diagnosed among aboriginal persons with a random sample of nonaboriginal persons diagnosed with TB, and evaluate the trends in rates of disease between both groups during the same period. DESIGN: A case-control study. SETTING: A provincial TB control program. PATIENTS AND METHODS: All patients with TB diagnosed among aboriginal persons in British Columbia between 1992 and 1996 were compared with control patients diagnosed during the same period. For each patient a control patient was identified. INTERVENTION: The demographic details, type of disease, bacteriology, risk factors for TB, therapy received as well as mode of administration were documented. The number of contacts identified for each patient as well as the number of patients completing chemoprophylaxis were identified. The rates of disease during the same period were also documented. RESULTS: During the study, 202 patients with TB were diagnosed among aboriginal persons and 201 controls were chosen. Apart from age at diagnosis (35.1+/-20 years versus 45.7+/-19.7), differences in the prevalence of lymphadenopathy (5.9% versus 16.4%, P=0.0008) and pleural disease (21.3% versus 16.4%, P=0.00008), there were no differences in presentation between aboriginal and nonaboriginal people. Aboriginal people were more likely to have a history of contact with a patient with TB (53% versus 17.9%, P<0.05), to have received directly observed therapy (55% versus 33.8%, P=0.00002) and to have contacts who were purified protein derivative (PPD) positive (4+/-9 versus 2+/-3, P=0.002). These contacts were more likely to start isoniazid (2+/-3 versus 1+/-1, P=0.002). Overall, there was a significant decline in rates of TB among aboriginal persons compared with the general population, but there was a small increase in rates among all subjects in the final year of the study. CONCLUSIONS: In the present study, significant variations in rates of TB among different population groups in British Columbia were found. During the study period, there was a greater decline in the rates of TB among aboriginal persons. A greater use of directly observed therapy and greater use of chemoprophylaxis occurred among aboriginal persons, which may have contributed to this decline, or alternatively, it simply reflects the natural evolution of the TB epidemic.

Exposure and sensitization to cat dander: asthma and asthma-like symptoms among adults.

BACKGROUND: Several pets, such as cats, dogs, and rodents, are known to produce allergens. Despite the clinical and laboratory evidence that exposure to pets can cause bronchoconstriction in sensitized subjects, the results of population studies have been contradictory. OBJECTIVES: The purpose of this study was to investigate the relationship between cat ownership and the prevalence of asthma, asthma-like symptoms, and bronchitic symptoms among subjects 20 to 44 years of age in Vancouver, Canada and to determine whether sensitization is responsible for such an association. METHODS: Two thousand nine hundred ninety-nine (88%) randomly selected subjects responded to a mail questionnaire. Of these, 504 participated in laboratory examination, including allergy skin testing. RESULTS: One thousand nineteen study responders (34%) were pet owners at the time of the study (current owners). Current pet owners were found to have a higher prevalence of current asthma, asthma-like symptoms, and bronchitic symptoms compared with those without pets. Cat owners had significantly higher risk of having current asthma and asthma-like symptoms. In the subset who had allergic skin tests, we found that those who were allergic to cat dander had a significantly higher risk of current asthma than those not allergic to cat dander and not owning a cat. CONCLUSION: This study provides evidence that sensitization to cat dander is a more important risk factor for current asthma and asthma-like symptoms than cat ownership itself.

T-lymphocyte responses to plicatic acid-human serum albumin conjugate in occupational asthma caused by western red cedar.

BACKGROUND: T cells are known to play a major role in the pathogenesis of atopic allergic asthma, but it is less clear whether they are involved in occupational asthma caused by low molecular weight chemicals such as plicatic acid. OBJECTIVES: We sought to determine whether peripheral blood T cells from patients with western red cedar asthma (WRCA) recognize plicatic acid (PA) conjugated to human serum albumin (HSA) as judged by proliferation or cytokine production and to analyze the response to PA inhalation with flow cytometry. RESULTS: Significant proliferative responses to PA-HSA were observed in eight of 33 patients with WRCA, none of 10 exposed nonasthmatic cedar workers, and one of 18 nonasthmatic control subjects. Two of 25 patients with WRCA also showed proliferative responses to unconjugated PA. All the WRCA responders were either currently exposed to cedar or had ceased exposure within the preceding 2 years. None of the four patients receiving oral steroids responded, but inhaled steroids did not seem to influence responsiveness. No correlations were found between the maximum stimulation response and any of the current FEV1 values, the current PC20 methacholine values, or the magnitude of the late asthmatic response to PA. Peripheral blood T-cell subset proportions and their degree of activation were similar in patients with WRCA and exposed control subjects. There was no change in T-cell phenotypes or their activation markers after PA inhalation challenge. In vitro, PA-HSA stimulation did not affect subset ratios but led to release of small amounts of IL-5 and IFN-gamma, with no detectable increase in IL-4. CONCLUSIONS: PA-HSA-specific T lymphocytes seem to be present in small numbers in the peripheral blood of patients with WRCA and may respond to antigenic exposure by producing IFN-gamma and IL-5. However, the proportion of responding cells would appear to be lower than in comparable studies of atopic asthma.

Risk factors for near-fatal asthma. A case-control study in hospitalized patients with asthma.

We prospectively recruited patients admitted to the hospital with severe asthma to comprehensively evaluate the association of historical and physiologic features with the risk of near-fatal asthma (NFA). A case-control study design was used. All patients admitted with NFA (cases) were identified prospectively and compared with asthma patients admitted during the same period without respiratory failure (controls). Nineteen cases (age: 40.2 +/- 12.0 yr) (mean +/- SD) and 80 controls (age: 36 +/- 13.5 yr) were enrolled. Duration of asthma, gender, smoking status, ethnicity, and prevalence of atopy were similar in the case and control groups. More than 80% of patients in both groups reported worsening symptoms for more than 48 h before admission, and more than 50% were worse for longer than 7 d. There was no difference in degree of airways obstruction or bronchial hyperresponsiveness (PC20). Perception of dyspnea was similar in the cases and controls, but among cases the males had greater impairment than the females (Borg score: 1.9 +/- 1. 4 versus 3.9 +/- 1.2: p = 0.05). Univariate analysis identified a history of previous mechanical ventilation (OR: 27.5; 95% CI: 6.60 to 113.7), admission to the intensive care unit (ICU) (OR: 9.9; 95% CI: 3.0 to 32.9), history of worse asthma during January and February (OR: 3.5; 95% CI: 1.0 to 11.8), and use of air-conditioning (OR: 15.0; 95% CI: 1.3 to 166) as risk factors for NFA. Of concern was the dependence of most patients (59.8%) on the emergency department (ED) for initial care, and the small number of cases (16%) in which patients visited a physician before admission to the hospital. We have confirmed risk factors identified previously in retrospective studies of fatal and NFA, and have also shown that hospitalized patients with asthma, irrespective of severity of their asthma, share several characteristics, especially in terms of their failure to respond to worsening asthma.

In vitro T-lymphocyte response and house dust mite-induced bronchoconstriction.

BACKGROUND: There is considerable evidence that T cells may play an important role in asthma. The purpose of this study was to determine whether the responsiveness of T lymphocytes to mite allergen stimulation in vitro is a determinant of bronchial response to house dust mite (HDM) allergen challenge in subjects who are allergic to HDM. METHODS: Peripheral blood was taken from seven healthy nonatopic subjects and 23 subjects with positive skin test reactions to HDM. Of the subjects in the latter group, 16 had an asthmatic reaction on inhalation challenge with HDM extract (HDM-responders), whereas the remaining seven had a negative reaction (HDM allergic). The proportion of subsets of T lymphocytes and their activation and the amount of IL-2, IL-4, IL-5, and interferon-gamma released in the supernatants with and without stimulation with the HDM extract were determined. RESULTS: Without stimulation, the proportions of subsets of T lymphocytes and their activation were similar between groups. When stimulated with the HDM allergen, the proportion of CD4+CD25+ cells from HDM responders was significantly higher than those in the control group. Comparison within groups of cell cultures with and without stimulation with the mite allergen showed that the proportion of CD4+, CD4+CD25+, CD4+/CD8+, and CD3+HLADR+ cells were significantly increased in HDM responders with stimulation; there was a trend for CD4+CD25+ cells to be increased in the HDM-allergic subjects; no increase in any T-lymphocyte subsets was found in the control subjects. The release of IL-5 was significantly greater in HDM responsers than in the other two groups. The severity of the immediate asthmatic reaction was significantly associated with the degree of nonallergic bronchial hyperresponsiveness and the amount of IL-5 released but not with the level of specific IgE to the mite allergen or subsets of T lymphocytes with and without stimulation. CONCLUSION: The findings suggest that responsiveness of T lymphocytes to allergen challenge in vitro may play a role in determining the bronchial response to the allergen in vivo.

Effect of application of benzyl benzoate on house dust mite allergen levels.

BACKGROUND: Several acaricides have become available for reducing house dust mite allergen levels. OBJECTIVE: The purpose of this study was to assess whether the use of benzyl benzoate (Acarosan) provides additional benefit to the usual mite control measures including encasement of mattress and pillows with vinyl covers. METHODS: A randomized controlled trial was carried out in 26 homes (14 control versus 12 treatment) of asthmatic patients in two cities (Vancouver and Winnipeg). The control group had the usual house dust mite control measures including the use of vinyl covers for mattresses and pillows while the treatment group had application of benzyl benzoate to mattresses and carpets in the bedroom and the most commonly used room, in addition to the above control measures. Mite allergen levels were measured 3 months and immediately before, 1 week, and 1 and 3 months after the application of house dust mite control measures. Patients kept diary cards on asthma symptoms and peak expiratory flow rates morning and evening one month before and three months after the onset of mite allergen control measures. RESULTS: A reduction of mite allergen level was found in mattress samples in both groups, statistically significant at all times in the treatment group and at one and three months in the control group. Mite allergen levels on floor carpets also showed progressive reduction in both groups, but were significantly different in the treatment group (compared with controls) at 1 week, and were lower compared with baseline in the treatment group up to 3 months. No significant changes in asthma symptoms, peak expiratory flow rates, spirometric measurements, or bronchial hyperresponsiveness were observed among treatment or control group subjects. CONCLUSION: The addition of benzyl benzoate to conventional house dust mite control measures resulted in a significant reduction in floor carpet dust mite levels that persisted for 3 months. The results of this study should be confirmed in a larger and longer study.