Background. In January 1994, the American Academy of Pediatrics recommended that annual screening with the purified protein derivative tuberculin skin test, Mantoux method, be used for tuberculosis screening in high-risk children. This test has a better sensitivity and specificity than the previously used multiple puncture test, and patients need to return for a reading done by palpation by a health care professional.
Objective. To estimate the prevalence of reactivity to purified protein derivative tuberculin in an urban primary care clinic whose patients meet high-risk criteria and to determine if annual screening is warranted, to determine the adherence to return to the clinic for reading of the skin test, and to describe the characteristics of patients who have tuberculosis infection and disease.
Research Design. Cross-sectional study.
Setting. Inner-city, hospital-based primary care pediatric clinic in Baltimore, MD.
Subjects. A total of 1433 consecutive children attending this clinic from March through September, 1994, who were at risk for tuberculosis because of frequent exposure to poor and medically indigent city dwellers.
Methods. The Mantoux test (5TU intradermal injection of purified protein derivative) was administered to children at annual health supervision visits. Patients were tracked to determine those who returned for a reading by a health care professional and find those with a positive Mantoux test. The charts of children with a positive test were reviewed.
Results. Five hundred seventy-three (40%) patients returned for a reading by a health care professional. Five patients had a positive Mantoux test, giving a prevalence rate of 0.8% of reactivity to purified protein derivative tuberculin. One child with a positive Mantoux test also had chest radiograph findings consistent with tuberculosis disease but was asymptomatic.
Conclusions. In our city with a low prevalence of disease, children whose only risk factor for tuberculosis was exposure to poor and medically indigent city dwellers did not represent a high-risk group. Our results are supportive of the 1996 American Academy of Pediatrics screening statement that annual screening is not warranted. Sixty percent of children did not return for a reading of the Mantoux test by a health care professional. Alternative strategies that are more convenient for parents are needed to obtain accurate readings by health care professionals when skin testing is deemed necessary.
- tuberculosis infection
- tuberculin skin test
- high risk
- resident continuity clinic
Since 1985, the number of tuberculosis cases among children in the United States has increased.1-4 The largest increase of 36% has occurred in children younger than 4 years from 1985 through 1992.3,5 In 1990, 86% of childhood tuberculosis cases occurred among minority populations. Access to acceptable medical care, overcrowding in the home, and tuberculosis in immigrant populations were proposed as possible explanations for this increase.5
In response to the increase in childhood cases, the Committee on Infectious Diseases of the American Academy of Pediatrics (AAP) had reevaluated the screening procedures for tuberculosis and in January 1994 recommended annual tuberculosis screening for high-risk children using the purified protein derivative (PPD) tuberculin test, Mantoux method.1 The committee defined children at increased risk for infection with Mycobacterium tuberculosis as those frequently exposed to the following adults: individuals infected with the human immunodeficiency virus, homeless persons, users of intravenous and other street drugs, poor, and medically indigent city dwellers, migrant farm workers, and contacts of adults with infectious tuberculosis.1,4,6
A change in the screening test from the multiple puncture test (MPT) to the Mantoux PPD was recommended because of improved sensitivity and specificity of the latter.1,6-8 The MPT test has been found to have sensitivities ranging from 68% to 97% and specificities of 40% to 90% when correlated with a Mantoux reaction ≥10 mm compared to the Mantoux test, which has sensitivities and specificities ≥90%.1,3,8,9 In contrast to the widespread use of the MPT where parents were asked to interpret the tests and mail results by postcard to the health care provider, interpretation of the Mantoux test requires a reading by palpation by a health care provider.1,6-8 The MPT had been the only screening test in pediatrics where the interpretation was done by a parent, not a health care professional.1,3 Yet tracking studies in our clinic had demonstrated that only 10% of postcard results were returned by parents to document the results of the MPT (pilot data), leaving 90% of patients for whom we had no information. Physicians may often assume that nonresponse by a parent means a negative test.3However, the need for palpation of the site by a health care provider necessitates a return visit to the clinic and may be inconvenient for parents.
Our clinic provides primary care for children in an inner-city pediatric clinic in Baltimore, MD. Baltimore has a low incidence of tuberculosis disease.10 Because our patients routinely meet the high-risk criteria of frequent exposure to poor and medically indigent city dwellers, we instituted annual screening using the PPD tuberculin test. Our study objectives were to (1) estimate the prevalence of reactivity to PPD tuberculin in an urban clinic whose patients meet high-risk criteria, (2) determine the adherence to return to the clinic for the reading of the skin test, and (3) describe the characteristics of patients who have tuberculosis infection and disease.
From March through September, 1994, all children who met the high-risk criteria of exposure to poor and medically indigent city dwellers were screened with the Mantoux test at scheduled health supervision visits. The identification of these children was at the discretion of the primary care provider. No parents refused screening. This above time period was selected as a response to the January 1994 AAP screening recommendation and ended when a sufficient number of patients had been screened. Nursing staff trained in the application of the Mantoux test injected 0.1 ml of 5 tuberculin units of PPD tubersol by Connaught (CT68) intradermally on the volar aspect of the forearm.11 The nursing staff logged the name and date of all patients screened. Parents were given verbal instructions, reinforced by written instructions, to return in 48 to 72 hours to have their child's Mantoux test results interpreted. If the test was applied on a Thursday and the 72-hour reading would occur on a weekend day when the clinic was closed, parents were instructed to return on the next Monday, 4 days later. Although the standard time for reading the skin test is 48 to 72 hours after the application, available evidence supports that the results are still useful after 5 days, but may lessen the diagnostic value of the PPD.12-14
Clinic efficiency measures were implemented to streamline return patients through the registration process and to enable them to have the test results interpreted within 10 minutes of their arrival. The reading of the test was limited to palpation of induration. The test site was carefully palpated by the nursing staff and if induration was present a pediatrician determined the limits of induration and measured the diameter using a ruler calibrated in millimeters.11When patients returned, the results were recorded in the log. Depending on whether or not they returned, participants were classified as adherent or nonadherent. We further classified nonadherers into three groups: (1) a caretaker who initiated a telephone call to give results (caretaker-initiated); (2) a pediatrician who initiated a telephone call to obtain results (pediatrician-initiated); or (3) phone contact was attempted with a family at least two times but they were unreachable (no contact). For caretaker-initiated telephone calls their interpretation of the results was recorded and parents were asked to bring the child in for a reading for any questionable results. Pediatrician-initiated telephone calls were attempted for the remainder of the nonadherers. Again, if any question existed about the results, the parent was asked to bring the child in for a reading by a health care professional. The no contact group included those families with whom no verbal communication occurred with any caretaker of the child despite the two attempts made to telephone each family.
The definition of a positive Mantoux test followed the AAP guidelines and depended on the risk characteristics of the child.1,6,7None of the patients included in our study were known to have been exposed to tuberculosis or were immunocompromised by human immunodeficiency virus or drugs. Thus, tuberculosis infection in this group was defined as a Mantoux test with induration of ≥10 mm and a negative chest radiograph. Therapy for infection included preventive treatment with isoniazid.3,6,7,15 Tuberculosis disease was defined as a positive Mantoux test and chest radiograph findings consistent with tuberculosis. Demographics of patients with a positive PPD test were determined by chart review that included age, race, size of induration of Mantoux test, date of prior screening, chest radiograph results and whether other high-risk criteria were present. Patients younger than 7 years with a positive Mantoux test were reported to the health department for associate investigation of family contacts. We contacted the health department several months after associate investigation was completed to determine whether other family members had infection or disease.
The demographics of the study population (Table 1) did not differ between those who returned for a reading by a health care professional (group 1), those where the caretaker initiated a phone call (group 2), those where a pediatrician initiated a phone call (group 3), and those who were not contacted (group 4). From March through September, 1994, 1433 patients were screened. Of these, 573 (40%) returned for a reading by a health care professional. Four patients in this group were found to have a positive tuberculin test. Eight-six children (6%) did not return for a reading but the caretaker initiated a telephone call and gave an interpretation by telephone. The parent of one patient in this group stated that the Mantoux test was positive, the patient was asked to come to the clinic and a positive result was confirmed. In 244 patients (17%), a pediatrician initiated a phone call and obtained a result over the phone from the caretaker in the household. For 530 children (37%), no information was available because the primary caretaker could not be reached despite two telephone call attempts to the home. No children were determined from the pediatrician initiated phone call group nor obviously from the group with no contact. A total of five patients were found to have a positive Mantoux skin test of ≥10 mm induration, resulting in a prevalence of 0.8% (5/573). None of the patients were found to have induration of <10 mm. In 60% of patients, the family did not adhere to the recommendation to return for a reading by a health care professional.
The characteristics of the five patients with a positive PPD reaction are listed in Table 2. All patients had been asymptomatic at the time of screening. The patients' ages ranged from 1.5 to 10 years. The only risk factor for the four African-American patients was exposure to poor and medically indigent city dwellers. The 5-year-old patient who had been born in Egypt and moved to the United States when she was 2 years old had an additional risk factor of birth in a country with an intermediate incidence of tuberculosis disease.16 Of note, 4 of 5 of the patients had had a negative screening test 1 year before. Two of these patients had had a negative MPT as the original screening test although an additional two patients had a negative Mantoux PPD. One patient who had a 5-mm PPD 1 year prior had a 15-mm area of induration 12 months later. The patient born in Egypt had had a bacillus Calmette-Guérin (BCG) vaccine at birth with two subsequent negative Mantoux tests, the last one 1 year ago.6 The four patients with a positive Mantoux test but a negative chest radiograph were started on isoniazid. Only 1 of the 5 patients with a positive Mantoux test had chest radiograph findings consistent with tuberculous disease. This patient was treated with isoniazid, rifampin, and pyrazinamide.3,6,7,15 Gastric aspirates were not attempted in this patient, because drug-resistant tuberculosis is rare in Baltimore.
The Baltimore City Health Department conducted associate investigation for children younger than 7 years (Table 2). In three of the cases, a household contact was found to have a positive Mantoux test—one adult in each of two cases, a child in the third case. None of these contacts had chest radiograph findings consistent with tuberculosis disease.
The rate of 0.8% in our study represents the highest possible infection rate among those children whose skin tests were interpreted. This rate was lower than the prevalence rate of 1% or more which is used to indicate a high-prevalence area where annual tuberculosis screening is warranted.3,17 The true prevalence in our study could be higher if a large number of positive cases existed in the nonadherent group who did not return for a reading by a health care professional. The demographics of this nonadherer group did not differ significantly from those who returned for a reading. However, studies by Howard12 and Cheng18 demonstrated that parents cannot reliably interpret the Mantoux test by palpation, suggesting that there may have been patients in the nonadherer group with positive tests. The true prevalence rate could also be lower than 0.8%, if none of the unread tests were, in fact, “positive.” The rate from our study is similar to that of 0.78% in New Orleans17 and 0.6% in Chicago19 found during routine screening. As a result, we determined a low prevalence of tuberculosis in our clinic population whose patients were considered high risk by 1994 AAP guidelines. Baltimore, however, is a unique geographic area. Because of the intervention of community-based, directly observed therapy, Baltimore has experienced the greatest decline in tuberculosis incidence of any city in the United States.10 The incidence rates of tuberculosis disease in adults is 17.2 cases per 100,000 population10 and 1.6 per 100,000 population in children in 1994 (W. Cronin, personal communication, State of Maryland Department of Health and Mental Hygiene). Baltimore tuberculosis infection rates are not available because infection is not a reportable condition in Maryland. Our study has demonstrated that children whose main risk factor was exposure to poor and medically indigent city dwellers in a community with a low prevalence of disease do not warrant annual screening. These data are supportive of the AAP's most recent screening recommendation.20 We have subsequently changed our screening policy to application of the Mantoux test at 4 to 6 years and at adolescence.1,6,20
Despite the low prevalence of tuberculosis infection, it was concerning that all patients had been screened 1 year before and four had had negative results—two with MPT and two with the Mantoux test. Because of the low prevalence of infection of 0.8% in our population, the positive predictive value of the PPD test would be low, approximately 8.8%.8 These reactions most likely represent false-positive results,3,8 probably due to cross-sensitization with nontuberculosis mycobacterium. Using the observed prevalence of reactivity to the PPD of 0.8%, the calculated annual rate of tuberculosis infection in our population is 0.1%, using methods of calculation by Styblo21 and Sutherland.22 Because the apparent annual conversion rate was 4/573 or 0.7%, higher than the calculated rate, the test conversions in our study are unlikely to have been caused by recent infection with M. tuberculosis. The patient from Egypt may represent boosting of tuberculin sensitivity from the prior BCG vaccine.23 However, other possibilities are that these patients had false-negative test results 1 year ago due to the low sensitivity of the MPT test, transient depressed cellular immunity with a viral infection, or factors associated with the tuberculin media, administration of the test, or factors affecting the reading.8,9 Another possibility is that these patients had recent exposure to tuberculosis within the past year. Information about tuberculosis in children supports that the younger the child, the more serious the morbidity, making early diagnosis important.3,4,15,24,25 With an incubation period of disease in infected children of 2 to 9 months, the period of greatest risk of progression to disease is the first year after diagnosis.24The rate of progression from tuberculosis infection to disease increases with decreasing age. Forty percent of infants with untreated infection develop disease within 2 years19,20 and 43% of infants infected in the first year of life will develop disease within their life if not treated, compared with 24% of 1- to 5-year-olds and 15% of 11- to 15-year-olds.3 Early identification of tuberculosis infection may be missed in cases similar to the ones we identified as we revert to less frequent screening as recently suggested by the AAP.20
Our study measured the adherence with a follow-up reading by a health care professional for screening with the Mantoux test. Forty percent of patients returned for a reading. This was higher than the rate of 10% in our clinic who had returned the MPT postcards, but it still left 60% of patients who had unknown or unconfirmed results. We wanted to measure the behavior of families when only verbal and written instructions were given; thus, we had not given any additional incentive to return, other than making the return process more efficient. Adherence rates vary from other sites. Sinai et al,26 in an inner-city Philadelphia clinic, reported a return rate of 25% for a reading by a health care professional and an additional 1% who called to report results (caretaker-initiated). Christy et al,27 in a Rochester urban clinic, reported a return rate of 64% by 48 to 72 hours, and an additional 11% by 94 hours. In Washington, DC, Cheng et al28 found that the rate depended on the intervention. Their initial adherence rate for an in-person reading was similar to ours at 45%. However, interventions such as written and verbal instructions for return, or linking the return of school forms contingent on visual interpretation, increased their rates to 60% and 66%, respectively.
Because the nonadherence rate was as high as 60% in our study, alternative strategies for screening must be investigated. Although Cheng et al28 improved the adherence by linking the test reading with return of school forms, this did not offer a more convenient strategy to parents. Extending clinic hours to evening and weekends would be convenient for working parents. Home visits have been considered, but the cost appears prohibitive. Another possibility is testing in schools or day care centers. Because children in these settings are a captive audience, the Mantoux test could be applied and a reading by a health care professional could take place in the school 3 days later. This mechanism would eliminate the additional inconvenience to parents because they would not need to take off from work to bring the child in for the reading. A decision cost-benefit analysis of school-based screening for tuberculosis infection found that targeted screening of high-risk patients defined as birth in a country with a high prevalence of tuberculosis, was 5.7 times more efficient than universal screening.29,30 One detriment to this school screening is that most cases of tuberculosis present in infancy and preschool; thus, school testing may be late. However, screening in day care centers remains an attractive possibility. Perhaps a combination of the above strategies should be considered. Clearly, more studies need to be done to examine the efficacy of these strategies to determine the way for the maximal number of patients to have Mantoux results interpreted by a health care professional.
We discontinued telephoning patients because we did not identify any positive cases or discern a benefit from this intervention. Telephoning involved staff time (approximately 1 hour/day), and a large number of parents (n = 530) were never reached. Although the telephone responsibility could be delegated to a trained health professional, we could not determine the accuracy of the information we received. For both caretaker-initiated and pediatrician-initiated calls, the parent might examine the arm, but the validity of the interpretation depended mainly on the parent's ability to palpate the arm for induration and give an accurate reading. As noted in a study by Howard,12only 37% of 212 patients with a confirmed positive PPD thought induration was present. Cheng et al18 found that only half of the parents appropriately identified induration in a group of patients with positive Mantoux tests. Through phone contact we have no documentation that the parent actually examined the Mantoux test site or just gave the easiest response when reached, a negative result. In the past, physicians have often assumed nonresponse to be consistent with a negative result. A nonresponse could mean that the parent forgot to look at the arm or forgot to telephone. Starke et al31reported that 20 of 150 Houston children with a positive Mantoux test had parents who had failed to report the results. To get accurate PPD readings, the site must be palpated by a health care professional.
No cases of tuberculosis disease were identified as a result of associate investigation. Because of the low rate of infectivity of tuberculosis in children, each child with a true positive Mantoux test represents exposure to an infected adult. Contact investigation remains an important mechanism to identify potentially infected and infective patients. Although the most efficient way of identifying infected children is through contact investigations of adults with pulmonary tuberculosis,3,9 the reverse, associate investigation, which includes tracking contacts of infected children, is also important. Some health departments perform associate investigations for children younger than 7 years. Most childhood risk factors for acquiring tuberculosis infection are really the risk factors of the adults in their lives.25 Some of the positive reactions to PPD tuberculin in our study may have been false positives, explaining why an index case with tuberculin disease was not identified. For the one child diagnosed with tuberculosis disease, associate investigation revealed an adult caretaker with a positive PPD but normal chest radiograph. This child attended a school for developmentally delayed children, and associate investigation could not be performed on all the attendants of the school.
Our study determined that the prevalence rate of reactivity to PPD tuberculin in children whose risk factors were exposure to poor and medically indigent city dwellers in a city with low prevalence of disease was low at 0.8%. Our results indicate that our patient population does not require annual screening, and support the revised recommendations of the AAP for periodic screening.20 Only 40% of children returned for a reading by palpation by a health care provider of their Mantoux test. Alternative strategies that are more convenient for families are needed to maximize test interpretation by health care professionals.
The authors appreciate the help of the Harriet Lane Clinic preceptors who telephoned parents to determine test results. This study was presented in part at the 35th Annual Meeting of the Ambulatory Pediatric Association, San Diego, CA, May 1995.
- Received December 7, 1995.
- Accepted May 31, 1996.
Reprint requests to (J.R.S.) Johns Hopkins Hospital, CMSC-143, 600 N Wolfe St, Baltimore, MD 21287–3144.
- AAP =
- American Academy of Pediatrics •
- PPD =
- purified protein derivative •
- MPT =
- multiple puncture test •
- HIV =
- human immunodeficiency virus
- Committee on Infectious Diseases
- ↵American Academy of Pediatrics, Tuberculosis, In: Peter G, ed. 1994 Red Book. Report of the Committee on Infectious Diseases. 23rd ed. Elk Grove Village, IL: American Academy of Pediatrics; 1994:480–500
- Starke JR
- Starke JR
- Kraut JR,
- Christoffel KK,
- Berkelhamer JE,
- Boddie-Willis C
- Committee on Infectious Diseases
- Styblo K,
- Meijer J,
- Sutherland I
- ↵Brailey M. Mortality in tuberculin-positive infants. Bulletin of the Johns Hopkins Hospital. Baltimore, MD: Johns Hopkins Press; 1936;59:1–10
- ↵Brailey ME. Tuberculosis in White and Negro Children: ll. The Epidemiologic Aspects of the Harriet Lane Study. Cambridge, MA: Harvard University Press; 1958
- Sinai LN,
- Chung EK,
- Case R
- ↵Christy C, Pulcino M, Lanphear B, McConnochie K. Tuberculosis screening in urban children. Arch Pediatr Adolesc Med. 1995;149:78. (Abstract).
- Cheng TL,
- Ottolini MC,
- Baumhaft K,
- Brasseux CO,
- Wolf MD,
- Scheidt PC
- Starke JR,
- ,Taylor KT, Martindill CA, Pyle ND, Herrin CM, Extremely high rates of tuberculin reactivity among young schoolchildren in Houston
- Copyright © 1997 American Academy of Pediatrics