Targeting tuberculosis testing: the yield of source case investigations for young children with reactive tuberculin skin tests

OBJECTIVE: This study was designed to determine the yield of investigations whose aim is to identify a source case for tuberculosis infection among tuberculin reactors 3 years of age or younger. METHODS: The authors describe the results of associate investigations conducted for child tuberculin reactors reported from January 1, 1996, through June 30, 1998. Associates were defined as individuals who live with or spend significant time with a child reactor. An associate investigation was defined as evaluation of at least one associate. A source case was an associate older than 10 years of age who had culture-positive, pulmonary tuberculosis during a period when the child could have been exposed. RESULTS: Two hundred seven children had an associate investigation performed with a median of four associates investigated per child (range 1-21). Birthplace was known for 187 (90%); 128 were U.S.-born. Of 1,222 associates identified, 980 (80%) were evaluated. Among 452 (46%) associates for whom birthplace was known, 250 (55%) were non-U.S.-born. Of 980 associates, 668 were household contacts; 198 (30%) were infected, three had prior tuberculosis disease, and three had active tuberculosis. Two active cases met source case criteria; the yield was 0.9 (2 of 207) source cases per 100 children investigated. Of 312 non-household contacts, 57 (18%) were infected and none had the disease. CONCLUSIONS: Although few source cases were identified for young tuberculin skin test reactors in New York City, investigations identified a proportion of cases and infection in associates similar to that identified among contacts to pulmonary tuberculosis cases. Such investigations may be identifying a high-risk group and should be considered, depending on program resources.     

Epidemiology of a tuberculosis outbreak in a South Carolina junior high school

A 13-year-old, female, seventh-grade student (the index patient) was found to have smear-positive, cavitary, pulmonary tuberculosis. Epidemiologic and contact investigation, involving skin testing over 900 people, revealed a 40 per cent tuberculin reactor rate for persons in the junior high school she attended compared to a 2 per cent rate for control schools. Repeat skin testing of initial non-reactors identified an additional 3 per cent of infected school children. School teachers showed a seven-fold increase in the prevalence of positive skin-test reactions following the outbreak. Tuberculin-reactor rates for seventh graders were substantially higher than for eighth graders. The more classes shared with the index patient, the higher the probability of being a reactor. Among students who shared no classes with the index patient, the highest rates of tuberculin reactions were found for those who had entered a classroom immediately after the index patient had left it. Evidence of transmission on the school bus and in the church choir was also suggested. Six secondary cases (three pulmonary) resulted from the outbreak. Identical phage types from the index and secondary patients suggest who had left school during the term proved useful in determining when transmission began. The index case was found to be a missed contact of a previously identified case of tuberculosis. Since household contacts are at high risk for developing active disease, there is a need for meticulous and complete investigation and preventive therapy for all such persons, especially children.     

Tuberculin reactivity in United States and foreign-born Latinos: results of a community-based screening program.

Because of the concern that we were underestimating the prevalence of tuberculosis within the Latino community in San Francisco, we undertook a community-based screening program directed largely towards recent immigrants. Of 1,871 intermediate-strength (5 TU) tuberculin tests applied and read, 37 per cent of the reactions were greater than or equal to 10 mm. Significant reactions were found in 53 per cent of foreign-born persons compared to 7 per cent of those born in the United States. Persons older than 20 years of age were more likely to have significant reactions compared to younger Latinos. Among the foreign-born, the frequency of significant reactions was not influenced by the length of stay in the US or a history of BCG (bacille Calmette-Guérain) vaccination. Two foreign-born children were found to have current tuberculosis. The prevalence of tuberculin reactors among US-born Latino children was 3 per cent, which suggests that undetected transmission of tuberculosis may be occurring. We conclude that Latino immigrants should be systematically screened for tuberculosis.     

The Ottawa County project: a report of a tuberculosis screening project in a small mining community.

Following a retrospective review of tuberculosis cases reported from Ottawa County, Oklahoma, from 1969 through 1973, a selective tuberculosis screening project was implemented. Screening of a "target group" of the population, 519 former miners, greater than or equal to 50 years of age, resulted in the discovery of abnormal chest X-rays in 182; (103 with silicosis, 36 with silicotuberculosis, 12 with inactive tuberculosis, and 31 with other abnormalities). Eighty-five of these persons had positive tuberculin skin tests. Preventive therapy was recommended for 50, and 36 completed the prescribed course of treatment. Eight new bacteriologically confirmed cases of tuberculosis were found and treated. A large number of persons (1,904) residing in the same area who were not part of the target group were also screened for tuberculosis. This group contained a large number of positive tuberculin reactors but very few were candidates for isoniazid preventive therapy. Thirteen persons in this group had abnormal chest X-rays consistent with inactive tuberculosis but 12 had been identified and given preventive therapy before the project began. These data suggest that selective approaches to screening for tuberculosis in a community which are based on an in-depth retrospective review of the tuberculosis case register can be highly successful.     

Childhood tuberculosis in North Carolina: a study of the opportunities for intervention in the transmission of tuberculosis to children.

New cases of tuberculosis in children continue to appear. A retrospective review of the medical records of a representative sample of such cases occurring from 1977 through 1981 was conducted to gain an understanding of why this preventable disease continues to occur in North Carolina children. Three per cent of cases were detected by routine screening; 17 per cent were diagnosed after the child's symptomatic presentation; and 80 per cent after contact screening. However, 14 per cent of cases detected by contact screening developed disease while receiving isoniazid prophylaxis for a positive tuberculin test; and 19 per cent of cases detected by contact screening developed disease while under surveillance, but not receiving isoniazid prophylaxis, as tuberculin negative contacts of known infectious cases. Adherence to accepted recommendations for prophylaxis should reduce the childhood tuberculosis case rate.     

Tuberculosis infection in urban adolescents: results of a school-based testing program.

In 1986-87 a pilot tuberculosis (TB) skin testing program was introduced for seventh and tenth grade students in the Boston (Massachusetts) public schools. The 8.9 percent tuberculin positivity rate in tenth grade students was significantly higher than the 5.1 percent rate found in seventh graders. A majority of those who were skin test positive were born outside the United States. These results suggest that tuberculin testing in an urban school setting may identify a significant number of candidates for TB preventive therapy, particularly among tenth grade students and those who are foreign-born.     

Prevalence of tuberculosis infection among primary school-entry children in Sydney

Abstract: A cross-sectional survey of 2044 Year 1 children enrolled in 24 primary schools was performed to determine the prevalence of tuberculosis (TB) infection. Of the 2044 children, 1458 (71 per cent) were Mantoux-tested and 1452 Mantoux reactions were read. Of the total, 6.5 per cent were Mantoux-positive; 17.8 per cent of overseas-born children and 2.8 per cent of Australian-born children were Mantoux-positive (relative risk for overseas-born 6.9, 95 per cent confidence interval 4.2 to 9.6). In the areas of Sydney where the study was conducted, there is a high prevalence of TB infection (noncontagious) among overseas-born children in the five- to seven-year age group. This indicates that there may be a large pool of infected children, a proportion of whom are at risk of developing active (contagious) adult-type TB in the future. These data, with other published data on TB infection rates in other age groups, can contribute to the estimation of the size of the infected pool in Australia to allow rational decisions regarding control of TB in Australia, including the possibility of introducing Mantoux screening and preventive therapy programs for high-risk groups.     

Prevention of tuberculosis in children: missed opportunities.

We conducted an eight-year prospective investigation in Tennessee of all cases of tuberculosis (TB) reported statewide in children younger than 15 years of age. Of the 109 verified childhood cases reported from 1981 to 1988, at least 23 (21%) were preventable. Eleven children developed the disease while they were under surveillance but were not receiving preventive therapy, nine cases resulted from failure of health care providers to conduct timely contact interviews/investigations, and three were due to other reasons. Improved surveillance, increased use of preventive therapy, and ensured compliance will contribute significantly to the elimination of tuberculosis in children at high risk of developing the disease.     

Substance use by indigenous and non-indigenous primary school students

OBJECTIVE: Recent Australian research with adolescents aged 13 to 17 years has found that Indigenous youth are more likely than non-Indigenous adolescents to smoke tobacco and cannabis, although they may be less likely to use alcohol. The objective of this study was to examine whether this pattern exists among younger children. METHOD: A school-based, self-report survey was conducted in primary schools that had high proportions of Aboriginal and Torres Strait Islander children. Four schools were located in metropolitan Brisbane and three in Far North Queensland (sample n = 507 students: 270 girls, 237 boys, aged 9-13 years). RESULTS: Significant numbers of these children had started to experiment with recreational drugs. Twenty-two per cent had attempted to smoke at least one cigarette, 14% smoked in the preceding year, while 3% had smoked more than 10 cigarettes in their lives. Thirty-eight per cent had had at least one drink of alcohol, while 6% had smoked marijuana at least once. There was no significant association between Indigenous/non-Indigenous background and risk of smoking tobacco or marijuana, while Indigenous children were less likely than non-Indigenous children to report experience with alcohol. CONCLUSIONS: Contrary to data from secondary school students, Indigenous youth in primary schools were not more likely than non-Indigenous children to have experimented with tobacco or marijuana, or to be frequent tobacco smokers. It appears therefore that the excessive uptake of drug use among Indigenous youth occurs in the early stages of secondary school. This finding underlines the importance of preventive education in primary schools, especially for Indigenous children who have a high risk of making the transition to drug use in adolescence.     

Preventive care: do we practice what we preach?

We used insurance claims from enrollees in the Rand Health Insurance Experiment to determine the amount of selected components of preventive care received by a representative sample of the non-aged population in the United States and to determine whether insurance coverage was an important determinant of that amount. Only 45 percent of infants received timely immunization for DPT and polio; 93 per cent received some well child care by 18 months of age. In the three-year experimental period, only 4 per cent of adults had a tetanus shot, 66 per cent of women aged 17-44 and 57 per cent aged 45-65 received a Pap smear, and 2 per cent of women aged 45-65 had a mammogram. Cost sharing was associated with even less preventive care: 60 per cent of children on the free plan and 49 per cent on cost sharing plans received preventive care of any type. For adults, women on the free plan received more preventive care of several kinds, and those aged 45-65 received more Pap smears than those on cost-sharing plans. Even with free care, most enrollees did not receive adequate preventive care. Thus, free care alone, while significant, is not a sufficient incentive to providing recommended levels of preventive care. The average per person insurance charge for increasing the amount of preventive care to a level consistent with that recommended would be $22 for a complete set of immunizations by age 18 months, $9 for a Pap smear every three years, and $97 for a Pap test and mammogram every three years.     

Recurrent tuberculosis: why do patients develop disease again? A United States Public Health Service cooperative survey.

In October 1983, a retrospective survey was initiated to determine if patients reported to the Centers for Disease Control as having recurrent tuberculosis truly had recurrent disease and, if so, why they had developed tuberculosis again. Twenty-three health jurisdictions provided information on 800 patients diagnosed as having recurrent tuberculosis during 1981 and 1982. We found that 199 (25 per cent) of the cases did not meet the criteria for recurrent disease. Of the remaining 601 recurrent cases, 20 per cent had no chemotherapy prescribed for their previous episodes of tuberculosis, 20 per cent were prescribed inadequate or inappropriate therapy, and 33 per cent were not compliant with their prescribed therapy regimens. Patients who, during their original episode of tuberculosis, received the major portion of their medical care from physicians in private practice were more compliant than those treated by other health care providers. However, those same patients were more likely to have received inappropriate therapy than patients treated by other providers. Better patient and physician education, closer monitoring, and greater use of preventive therapy and directly observed therapy are necessary to resolve these problems.     

A Quantitative Benefit-Risk Analysis of Isoniazid for Treatment of Latent Tuberculosis Infection Using Incremental Benefit Framework

BackgroundWe undertook a quantitative benefit-risk analysis of a targeted isoniazid (INH) therapy for latent tuberculosis (TB) infection for different groups of contacts of active TB cases.MethodsWe developed a decision-analytic model to compare the treatment of latent TB infection in subgroups of contacts to no treatment over a 6-year time horizon in a Canadian setting. Contacts were stratified into 32 groups on the basis of five binary variables: type of contact (close or casual), tuberculin skin test (TST) results (positive or negative at 5 mm cutoff), Bacillus Calmette-Guérin vaccination status, place of birth (foreign- or Canadian-born), and age group (cutoff 35 years). Risk of TB reactivation was calculated for each subgroup from a longitudinal registry of contacts, adjusted for several potential confounders and comorbid conditions. We calculated the quality-adjusted life-years gained because of delayed or prevention of active TB via treatment of latent TB infection versus quality-adjusted life-years lost because of the adverse events to INH.ResultsA targeted policy based on adopting INH therapy only in subgroups with positive expected incremental net health benefit resulted in a different treatment decision than the current guidelines in five subgroups comprising 3.9% of the contacts. Namely, the targeted policy comprised no INH therapy in casual contacts with a positive vaccination history even with a positive TST result and INH therapy in foreign-born close contacts younger than 35 years even with a negative TST result.ConclusionsFrom a benefit-risk viewpoint, INH treatment of contacts should be tailored on the basis of risk assessment algorithms that consider a range of factors at the time of screening.     

Idiopathic thrombocytopenia in childhood. Edinburgh experience 1962-82

This retrospective review of 136 children with idiopathic thrombocytopenia assesses the prognostic significance of various presenting parameters and the effect of therapy. Initial haemoglobin, white cell count, actual platelet count, splenomegaly, hepatomegaly and lymphadenopathy had no significant effect upon the final outcome. Cases of acute I.T.P. were associated with a higher incidence of preceding infection, a shorter history of bleeding and a preponderance of males. The presence of greater than 20 per cent lymphocytes in the bone marrow was associated with a longer time to achieve a normal platelet count (p = 0.05). Steroid therapy shortened the time for acute cases of I.T.P. to obtain a normal platelet count (p = 0.05), but had no effect on long-term prognosis. Chronicity occurred in 25 children (18%) and nine of these had spontaneous remissions. Immunosuppressive therapy was ineffective, but nine out of 12 children were cured by splenectomy. Mortality was 0.7 per cent (one death) and general morbidity was low.     

The duration of BCG-induced tuberculin sensitivity in children, and its irrelevance for revaccination. Results of two 5-year prospective studies

It had been shown earlier, in a retrospective study, that tuberculin sensitivity is stronger in children tested for the second time after vaccination than in those tested for the first time after vaccination. The hypothesis that the tuberculin test itself may reinforce sensitivity to a further test has now been confirmed in 2 strictly controlled prospective studies, which are reported here. The results refer to the tuberculin reactions 5 years after vaccination. These reactions were significantly larger in children who had had an intermediate test (less than 5 years after vaccination) than in those tested for the first time at 5 years. This was found equally for several BCG products, but there was a significant tendency for the PPD batch RT 19-20-21 to have a more pronounced effect than the other tuberculins.     

A survey of aspirin use and Reye's syndrome awareness among parents.

A national telephone survey of 1,155 parents of children 19 years of age and younger solicited patterns of medication use during episodes of childhood flu and chicken pox. During the previous two years, 6 per cent of the parents whose children had chicken pox and 16 per cent of parents whose children had flu administered aspirin. Approximately 12 per cent of the total sample said they would give their child aspirin if their child were to get the flu or chicken pox today. About half (53 per cent) were aware of the contraindication against aspirin use and 40 per cent could spontaneously recall the name Reye's Syndrome (RS). When measured by a recognition test, 84 per cent of the sample said they had heard of RS. People who continued to believe that aspirin was an appropriate medication were more likely to have treated older children. The RS contraindication for aspirin should be emphasized for teenagers in future public informational programs.     

Aseptic meningitis due to echovirus 4 in Panama City, Republic of Panama

Between September 23 and November 30, 1981, 1,032 children from Panamá City, Republic of Panamá were hospitalized with aseptic meningitis. Forty-four per cent of the cases were in the age group 5-9 years old; the disease was mild and self-limiting with an average hospital stay of five days. Echovirus 4 isolates were obtained from 48 of 160 patients. To identify risk factors associated with the epidemic, the authors randomly selected 10 per cent of hospitalized cases and conducted a family-based seroepidemiologic study. The closest neighboring house with at least one child younger than 15 years was similarly studied as a control. In total, 182 households and 1,083 of 1,177 residents were included. No risk factors ascertained by the study were associated with aseptic meningitis; however, several factors were related to recent echovirus 4 infection. Overall, 56 per cent of cases had echovirus 4 antibody, as did 29 per cent of their family members and 19 per cent of control family members. Children who attended kindergarten or primary school were more likely to have antibody than other household members and, within case families, individuals involved in child-care had an excess risk for infection.     

The cost-effectiveness of evidence-based guidelines and practice for screening and prevention of tuberculosis

INTRODUCTION: The potential cost-effectiveness of screening depends on the risk of tuberculosis (TB) in the population being screened and the rate at which the screening outcome (prevention) is achieved. AIMS: To compare the cost-effectiveness of contact screening for TB for: (1) contact screening as it actually occurred in Victoria in 1991 (Model 1); (2) the process which should have occurred had the 1991 contact screening guidelines been followed (Model 2); (3) a hypothetical evidence-based model (Model 3). METHODS: Three models were constructed according to the aims. The cost-effectiveness of contact screening is presented as costs to government per unit outcome (in the form of cases prevented, cases found and contacts traced) for each model. Assumptions about disease behaviour were consistent between models. A sensitivity analysis was performed to examine the effect of the assumptions made in Model 3 about rates of referral and treatment of infected contacts, and about the efficacy of isoniazid (INH) in preventing TB. RESULTS: The total cost of Model 1 was greater than that of the other Models. Model 1 is the least cost-effective, costing $309 065 per case prevented, and Model 3 is the most cost-effective, costing $32 210 per case prevented. The cost of Model 2 was $58 742 per case prevented. The incremental cost-effectiveness of Model 3 compared to Model 2 is $107 per additional contact screened, and $3881 per additional case prevented. Case finding is not as cost-effective as best-practice case prevention, ranging from $231 799 per case found in Model 1 to $205 596 per case found in Model 2. The sensitivity analysis shows that the cost-effectiveness of Model 3 decreases with lower referral rates, lower rates of preventive therapy, and lower efficacy of INH. However, even allowing for reduced programme parameters, Model 3 is most cost-effective. DISCUSSION: Costing policy options is an important component of programme delivery, but needs to be considered in the context of the product being purchased, e.g. the prevention of disease, or case finding. Case finding as a product of contact screening is expensive in all three models. Prevention of TB, on the other hand, can be cost-effective, as shown in Model 3. It was least cost-effective in Model 1, largely because prevention was not considered a priority, and few infected contacts actually received preventive therapy. Clear programme aims, adherence to guidelines and high rates of preventive therapy are essential in order to achieve cost-effectiveness.     

Health status of Ethiopian refugees in the United States.

The health status of 239 Ethiopian refugees in the United States was evaluated. Over 70 per cent were males 15-30 years old. Positive PPDs (purified protein derivative of tuberculin) were observed in 72 per cent and 3.4 per cent had abnormal chest x-rays. One patient had active tuberculosis. Other laboratory abnormalities included: intestinal parasites (36.7 per cent), anemia (14.9 per cent), eosinophilia (14 per cent), positive syphilis serology (7.5 per cent), and hepatitis B surface antigenemia (9.4 per cent). The most prevalent intestinal parasites were Giardia lamblia, Trichuris trichiura, and Schistosoma mansoni.     

Ascorbic acid status of children with developmental disabilities.

Ascorbic acid status of thirty-nine white children with developmental disabilities, ages three to nineteen years, is reported. Mean daily ascorbic acid intakes were calculated from three-day food records. Biochemical assessment consisted of fasting serum levels and a 6-hr. load test. Nine children served as a control group for the load test only. Mean dietary intakes for the vitamin were 204 per cent of the allowance. The mean serum ascorbic acid value was 1.3 mg. per deciliter. Only two children had levels at the unacceptable deficient level. Following load tests, ten children were identified as low excretors (less than 17 per cent), nine were moderate excretors (17 to 23 per cent), and the rest were high excretors (above 23 per cent). All of the normal children were high excretors. Two of three children with low ascorbic acid intakes (below 66 per cent of the recommended allowance) were verified as deficient by their fasting serum levels and urinary recovery after a load.     

Haemolytic-uraemic syndrome in Western Australia, 1980 to 1994

Abstract: A retrospective, population-based study of patients hospitalised with the haemolytic-uraemic syndrome in Western Australia from 1980 to 1994 was undertaken to describe the epidemiology of the disease in this state. We identified 41 patients. Episodes were commonest in children under five years of age (63.4 per cent) and were more frequent in females (58.5 per cent) than in males; only one Aboriginal patient was detected. More than 90 per cent of episodes had a gastrointestinal prodrome lasting from one to 22 days; in 47.6 per cent of these episodes patients had bloody diarrhoea. The average hospital stay was 26 days, and 63.4 per cent of patients required dialysis (mean 10 days). More than 20 per cent of patients developed chronic renal failure, 9.7 per cent died, two patients developed hypertension and one child became epileptic; three of the 10 patients over 16 years of age (30 per cent) died. The haemolytic-uraemic syndrome is potentially fatal, affects mostly young children, and is usually preceded by a gastrointestinal illness. Episodes can occur in common-source outbreaks but, with the exceptions of related cases in families, that appears not to have been so in Western Australia since 1980. There is a need for increased awareness of the haemolytic-uraemic syndrome to enhance prospects for earlier detection and better clinical outcomes. Improved public health surveillance is also needed to reduce the risks of the syndrome in the community.