Article Text

The association of diabetes and tuberculosis: impact on treatment and post-treatment outcomes
1. Roshani N Sanghani1,
1. 1 Department of Endocrinology, Hinduja Hospital and Research Center, Mumbai, India
2. 2 Department of Pulmonary Medicine, Hinduja Hospital and Research Center, Mumbai, India
1. Correspondence to Dr Zarir F Udwadia, Department of Pulmonary Medicine, Hinduja Hospital and Research Center, Hinduja Hospital, Mumbai 400020, India; zarirfudwadia{at}gmail.com

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One woe doth tread upon another's heel, So fast they follow. William Shakespeare. Hamlet. Act 1V Scene V11

Thus there is now incontrovertible evidence that TB and DM are linked in a danse macabre. Diabetes triples the risk of developing TB and this chronic non-communicable disease has now emerged as a powerful risk factor for one of mankind's most ancient infections. A strong case can and should be made for integrating TB and DM care. All confirmed TB patients should be systematically screened for DM and all diabetics should be actively screened for TB at least when they are symptomatic. Is screening for TB among diabetics likely to yield results? In a systematic review of literature Jeon10 demonstrated that screening of diabetics yielded active TB prevalence rates ranging from 1.7% in Sweden to 36% in Korea with TB being more common (prevalence ratios as high as 21) in those with insulin dependence compared with those with milder DM.11 Screening would have higher yield in a country like India where TB prevalence is estimated at 283/100 000. In this high-prevalence setting, screening 90–350 people with DM would yield one or more cases of TB. DM patients should be questioned about chronic cough (lasting >2 weeks) at the time they are diagnosed with DM and ideally at each regular follow-up. Those with positive TB symptoms should be examined as per national guidelines.

Conversely, what about screening for DM among TB patients? When all the studies that screened for DM prior to TB treatment were looked at, the prevalence of DM ranged from 8.6% in Turkey to 19.8% in Pakistan. In the setting of Mexico with among the highest DM baseline prevalence rates of 10%, it would be bad practice not to screen all TB patients for DM since screening as few as 2–10 TB patients would yield at least one additional case of DM. Indeed the prevalence of TB in screened DM patients is commensurate with estimates for other populations in which active case finding is recommended such as HIV-infected individuals, gold miners in South Africa and prisoners in developing countries. Questions remain about the optimal timing of screening for DM. Active infection with TB may temporarily elevate blood glucose levels and the timing and choice of screening methods remain important unanswered questions.

Acknowledging the importance of bi-directional screening for TB and DM the WHO and the International Union Against Tuberculosis and Lung disease (IUATLD) released a landmark document in 2011 acknowledging this association and calling for increasing integration between DM and TB control efforts.12 Without integrated care this burden of DM threatens to sabotage attempts to meet the United Nations Millennium Development Goals of TB control. At the same time additional funds are of course needed. India for example, has the highest burden of TB in the world (accounting for 20% of the global incidence) and houses around 58 million diabetics. Unfortunately in India, the optimal spending needed for each patient with DM exceeds by three times the amount being currently spent and these additional costs would overwhelm most TB control programmes.13 Consider the South East Asia (SEA) region: Sullivan showed that if all the 3–5 million estimated cases of TB in the SEA region in 2010 were actively screened for DM, an additional 66 500–1 225 000 diabetics would be detected.14 The cost of treating these additional diabetics through the 6-month duration of Directly Observed Therapy Short Course (based on estimates from India of US$149 direct cost per patient) would amount to an additional cost of US$5–92 million.15 The long term funding of DM care and the management of its complications after the TB is treated is an even more vexatious issue. Many unanswered questions remain but well conducted prospective studies like the one by Jimenez-Corona are beginning to illuminate the path.

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## Footnotes

• Contributors Both authors contributed equally.

• Competing interests None.

• Provenance and peer review Commissioned; internally peer reviewed.

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