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Tuberculosis issues in Asian Schools

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  • Tuberculosis issues in Asian Schools

    Some information when it comes to dealing with school age children and their teachers in Asian schools. Dealing with an infected teacher:

    This whole TB approach thing here in Thailand has been puzzling to me for the past six months, considering what a great medical care system the country has, and its "different" approach to the treatment of TB infection. I first ran into this bit of a conundrum when I approached some young Thai physician at Bangkok Phuket Hospital concerning an evaluation for myself, after being in a TB endemic area of the Philippines over Christmas. I had a post infectious flu bronchiolitis which I was recovering from, but I had wanted to know what their approach to diagnosing TB infection was. To my surprise, the young doctor recommended chest X ray and sputum evaluation. He had no idea what I was talking about when I suggested a simple TB PPD skin test, or, a blood test which is commonly used in the USA (the Quantiferon TB test and it's IGRA analogues). He said that they didn't do that, nor did he know anything about TB blood tests. This is common basic knowledge in the US medical system, and its use is the gold standard for analyzing possible TB infection. I was quite surprised.

    I can now see that the Thai approach to analyzing possible TB infection is far more relaxed than what we would encounter in the west. Let's talk about some facts, which will clarify why this "good news" is no news at all.
    • The timing for these children to show infiltrates or other signs of pulmonary TB is off. Considering that this teacher, who no doubt is closely watched by her associates, allegedly just started having symptoms prior to vacation (and therefore was infectious sometime before), for these children to develop active pulmonary disease so quickly is a bit of a stretch. It's possible, just not probable that anything would be evidenced by chest films at such an early stage of this exposure. Not to say that the approach was wrong; more appropriate to say that positive results would not be expected in this age group at that time.
    • The fact that Thailand diagnoses active TB via sputum collection and chest x ray leads one to suggest that this teacher had positive sputum and an obvious lesion on her chest film. People with active TB who have positive sputum on their gram stains are far more infectious than those with negative sputum smears; patients with cavitary lesions on chest x ray are far more infectious than those with simple infiltrates or nodules. As we are not privileged for that information, we have no idea how infectious this teacher was; one must err on the side of caution and suggest that she was infectious because her work up was positive for TB. Of note, this teacher may have been highly infectious prior to her developing cough; singing is a well known transmitter of infected aerosolized particles, and no doubt, this was one of the activities in the preschool area. Also, frequency and severity of cough does not necessarily correlate with how contagious a patient might be. It is generally accepted that patients should be considered to be infectious for the three months prior to their TB diagnosis (and quite possibly, longer).
    • Sputum collection is notoriously "impossible" in children this age. They don't have the chest wall mechanics to generate enough force to expectorate sputum, and whatever sputum they might have, provided that they actually do have active pulmonary TB, is usually swallowed. The method for analyzing children of this age to to do gastric lavage, usually via an orogastric tube. Even then, success rates at discovering mycobacterium is around forty percent or less. To state that the children's sputum evaluations were negative is meaningless.
    • Of more importance is the fact that children of this age generally and typically develop a more invasive form of TB, instead of the more commonly found pulmonary TB that we see in adults. The mycobacteria invade the lymphatic system and eventually get blood borne, resulting in more disseminated disease. These bacteria can go anywhere in the body, but generally it ends up in blood rich organs with higher serum blood oxygen levels. Miliary TB is when this infection infects various organs and skin throughout the body, osseus TB is when it invades the bones, usually the more blood vessel rich areas of the long bone growth plates and the spine. Abdominal TB is when these organisms invade various intestinal areas, usually the terminal ileum and parts of the colon and sometimes the peritoneum leading to widespread abdominal disease. The genitourinary system can also be infected. Of most concern, when these mycobacteria settle into the blood rich area of the subarachnoid space at the base of the brain, meningeal TB can occur. All of these invasive forms of TB tend to be more lethal, especially the meningeal version, and all of these forms of invasive TB tend to be more commonly found in children, as, it is presumed, their immune systems and cell mediated immunity cells don't isolate the mycobacterium in the lungs as well as adults do.
    Negative chest films and sputum are welcome, but quite frankly, it should have been expected. It is a common approach however, and it is more successfully used in adults who tend to get pulmonary TB. But as for clearing these young children, it is not adequate.
    Some facts about how this affects kids and how it relates to their classroom:
    • The invasive forms of TB are more common among children below the age of five. Children five and below are considered to be "high risk" for TB infection. Adolescents and young adults are also at higher risk for developing active TB from latent infection.
    • TB infection in children aged five through fifteen years is uncommon in the USA most likely because of the increased adherence to testing and eradication policies.
    • Child to child transmission of TB is uncommon due to their minimal sputum production and tendency to develop TB forms other than pulmonary. However, it has occurred and is possible.
    • Various countries, including Thailand, try to ward off the devastating invasive forms of TB by administering the BCG vaccine (Bacille Calmette Guerin) immediately upon birth. This vaccine allegedly pretty successfully prevents the more invasive forms of TB that children are susceptible to, however, it should be noted that it does poorly at preventing pulmonary TB, and there is some controversy concerning how successful it is at warding off the more invasive blood borne TB infections. Various studies have had various outcomes, which has led to the controversy about this vaccine. Regardless, Thailand uses it, and no doubt, its use has played a part in how the Phuket Health Administration has approached this problem (from what I can tell from your email, and from what people have told me).
    • Not all countries use the BCG vaccination, the US in particular, does not. The rate of TB in the US is very low, and the success at preventing TB with the vaccine is a little controversial, so it is not common practice to vaccinate in that country. Britain and other European countries used to use BCG, as well as most countries that have a high TB prevalence, such as Thailand, which continues to do so. The US tends to lean more towards an "eradication of latent disease" policy, than a "treatment of active disease" policy.
    • PPD skin testing for TB is the gold standard, regardless of BCG vaccination history. It is true that prior BCG vaccination can trigger false positives with tuberculin skin testing, however, this effect fades over time, with adults responding as expected with PPD skin testing regardless of BCG vaccination. Children, even though vaccinated, can demonstrate a positive response to PPD skin testing, though one must take into account the type of exposure, the amount of induration post test, and other health factors. PPD skin testing is still the first approach to investigating TB exposure and possible infection.
    • The type of exposure is important when deciding how to treat exposed individuals, as is their health status and their age. The proximity to someone who has active TB is very important; it is generally accepted that family members of a patient with active TB must also undergo the same antibiotic regimen as the patient. It is generally accepted that these family members are infected and active as well. In the case of other situations, the type of exposure must be taken into account. An enclosed space with minimal sunlight (UV radiation), and minimal outside air changes is more of a risk than exposure to someone with active TB in an outdoor environment, or, in an enclosed environment with open windows and plenty of fresh air. The mycobacterium live in micron sized moisture particles that are exhaled by the patient with active TB; these particles, protected from outdoor sunlight, can endure and float around an enclosed room for upwards of six hours (and more). The classroom in the ECC in which this teacher worked would be considered a closed high risk environment due to the low turnover of outdoor fresh air (an enclosed space is considered "safe" if it has more than six room-air changes per hour). The cafeteria in which she ate, due to the open nature, is much less so. Even then, close contact with her colleagues has to be taken into consideration; it can only take around ten mycobacterium to start an infection in the lung given the right conditions, and there can be upwards of hundreds of bacteria in an inhaled aerosol droplet. Considering that a person with active pulmonary TB can produce a cough with three thousand infective droplets, you start to get the idea as to how communicable this can be, especially in an enclosed space. Oh, and those paper surgical masks that people wear? Useless. After fifteen minutes of breathing through them, the exhaled moisture destroys the filtration ability of the masks. (Remember that the next time you stand close to a coughing individual with a mask).
    An interesting historical aside with respect to spaces and TB. In New York on the upper East side, we had an old TB sanitarium from the early 1900's. Large building, multi-story, and all built with no exterior corners. All the corners of the building were constructed in a round shape with plenty of windows, all the patient wards were large open spaces. It's interesting to note that the people who managed TB back in the days before these specifics of transmission became known, knew enough that corners yielded dark spaces, small rooms induced close contact, and plenty of windows allowed fresh air turnover inside, along with sunlight...
    • The health and age of the people exposed is important when evaluating possible infection of TB. Malnourished individuals and those with a low body weight to height ratio, whether through illness or self-inflicted diets (such as veganism, etc.) can lead to diminished immune function. Treatment for cancer, treatment with steroids, other types of medications, and age, are also factors. The elderly are more at risk, and children from age 5 and below are always considered to be high risk. In children younger than age five, TB disease is more likely to occur; the latent period after TB infection is briefer, and the disease tends to be more invasive and lethal. Considering the fact that these children who have been exposed to this infected individual are high risk, and were in a high risk environment, it would be considered by most physicians that these children would have to be treated just as a family member would. That's a big step, and a more reasonable and tempered approach, would be to at least skin test them to see if they had been infected.
    What is usually done:
    • All children and adults who have been exposed to this individual would undergo PPD skin testing. The use of chest x ray and sputum analysis rules out active disease but does not rule out latent infection. PPD skin testing is performed again at twelve weeks post exposure in case of initial tests being negative.
    • PPD skin tests in children can be unreliable at first. If positive, the significance of which demonstrates infection (latent disease) but not necessarily active disease, children (and adults) would be treated with one antibiotic, usually INH (Isoniazid) for a period of six to nine months, depending upon the protocol used. The purpose of treating these children is to destroy the disease before it becomes active. Remember, children tend to develop more invasive blood borne disease than adults, the results of which can be lethal. These blood borne versions of TB can be harder to diagnose, as children with for example, meningeal TB, will initially present with fevers, lethargy, "not acting right", some weight loss, progressing sometimes over a period of two to three weeks, to altered mental status, cranial nerve abnormalities, paralysis, coma and death. This form of TB disease tends to start in children anywhere from three to six months after initial exposure and infection. It's not always an easy diagnosis to make, and generally not one that is initially thought of when dealing with a feverish child that "doesn't act right". Fortunately, it is rare, but when it occurs, it can be highly lethal. This is why, at least in the US, skin testing to decide infection, and then eradication of the infection before it becomes active, is the gold standard.
    • PPD skin testing should be administered via the Mantoux method; the older TB tine test is unreliable. There are blood tests that can also be used; the interferon gamma release assay tests (IGRA, Quantiferon TB and related) can be substituted, but their use in children is not as extensive as that in adults. I do not believe the IGRA blood tests are available in Thailand.
    • INH treatment of latent infections in children is virtually one hundred percent successful in eradicating TB disease with minimal to no side effects. It is less successful in adults, being only fifty to eighty percent effective. More side effects, predominantly liver related, are found in older patients and especially those who imbibe alcohol. There are other treatment regimens for adults that can be used.
    • Children's initial skin testing might be negative, as their immune systems are slower to respond to the mycobacterial invasion. They can take up to twelve weeks after exposure to turn positive. Sadly, during this time, some children can develop meningeal TB prior to the end of the twelve-week period. They can develop systemic disease prior to the second skin testing. Which is why vigilance in this population is very important.
    • Any child that converts positive on PPD skin testing gets INH treatment. Any child that develops active disease, or, is in a family of someone with active disease, gets the full blown four antibiotic regimen. Any child whose skin test is initially negative is tested again at twelve weeks; if that test is negative, the child is clear. If not, the child needs to be treated for latent infection with the INH regimen or similar.
    • The American Academy of Pediatricians, and the American Society of Thoracic Surgeons, along with other major medical organizations, will automatically treat all children under the age of five with INH if they have been in "close contact" with a patient with active TB.
    • In case of questionable results on skin testing, or, for confirmation, there are blood tests available. The Quantiferon TB blood test is highly sensitive and specific regardless of prior BCG vaccination, and is generally recommended for those potential patients who have been previously vaccinated. It is also recommended for children, but it does not have as extensive a track record of usage as it does with adults. Because of the high-risk nature of lower age children, a positive skin test, or a history of "close contact" generally warrants INH treatment to eradicate the disease before it can become active (and therefore, communicable, and potentially lethal)
    • The usual progression rate to active TB in people exposed to those with active TB is usually about ten percent, in a general population in the west, so this usually is not an easy disease to get. Healthy people can overwhelm the initial infection. People who develop active disease tend to so within two years of the initial infection. However, again, proximity and duration of proximity to the affected, along with that individual's health status, are significant. The general movement in this community towards veganism, vegetarianism, raw foods, and other less nourishing activities ironically plays a negative role in community health, when considering the fact that we live in a country with one of the highest TB rates in the world.
    • Interestingly, if you speak with some of the older, more experienced pediatricians at Bangkok Phuket (a private institution, not public), they tend to agree that skin testing is absolutely necessary. Their approach to this is similar to how this would be dealt with in the US and the western world.
    The Thailand TB enigma explained:
    • Which brings me to why this is being treated the way I think it is being dealt with. Thailand vaccinates everyone and doesn't skin test children (which generally should be done in all school age children at age 6 and again at 10 or 12. Teachers and others with significant exposure to children should be skin tested more regularly). Thailand doesn't do this, and they seem to train their younger doctors towards this end. The reason most likely being, that if they did skin test the millions of school age children they have in this country, they would be overwhelmed with positive skin test results. The approach here seems to one of waiting it out and seeing who develops disease, and then treating it. With most healthy individuals not developing active disease after infection, treating who develops disease is one way of dealing with the overwhelming presence of TB here. Treatment of active disease, and not eradication of infection to prevent active disease. It's cheaper, and easier to deal with. Granted, some kids are going to fall through the holes here, develop significant disease and possibly die because of it, but, given the overwhelming presence of infection here, I assume they feel this is the best way to go. It's their country, they can do what they want with it. It also explains Thailand's very high ranking internationally with respect to TB infections.
    • I don't think that the western parents paying high prices at an international school, who are used to the best approach in medical care, would agree with Thailand's approach. Personally, I don't. Especially the parents of low age children who have not been BCG vaccinated. There should be concern among parents of BCG vaccinated children also, due to the variability in that vaccine's effectiveness.
    The school has been placed in this situation by a governmental approach to an infectious disease that does not correlate with the more commonly accepted (and better) western approach. Most parents are going to want what's best for their kids, most parents are going to expect western education and western health care even though we live in an Asian country. If chest x rays and sputum collection on five-year olds is all that the Thai government is going to recommend, again, they're acting in a "treat the active infection" mindset and not the "eradicate the disease" one. Yes, statistically and theoretically, most if not all children should escape this conundrum unscathed, at least, we all hope so, assuming that all children here are vaccinated, and also assuming that the vaccines here are effective. But remember, not all children here are BCG vaccinated (and the efficacy of BCG vaccination is debatable and controversial in various countries), and therefore, the actual risk is hard to quantify. And all western medical organizations agree that young children are high risk by nature and should therefore be treated aggressively.
    The costs for skin testing are minimal, and the risks are absurdly low. The benefits of testing and treating appropriately far outweigh the risks of developing disease.

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