Fw: (LML) Contact examinations to identify new cases

 

Leprosy Mailing List – December 10,  2020

 

Ref.:  (LML) Contact examinations to identify new cases

 

From:  Paul Saunderson, Ålesund, Norway

__________________________________________________________________________________ 

Dear Pieter,

I planned with several colleagues to submit this letter to PLoS NTDs, but it appears they no longer accept letters to the Editor!  I hope that you will be willing to post it on the LML and thus perhaps reach the right audience by an alternative means.

 

Leprosy case-finding through contact examination should include as many contacts as possible

A recent paper in PLoS NTDs presents long-term follow-up data on contact examinations to detect new cases of leprosy in Bangladesh (1 - the paper is attached for easy reference).  Together with previous publications from the same study, an interesting picture can be built up of the dynamics of leprosy transmission in and around households (2, 3).

Regarding the most recent paper, however, we disagree with the interpretation of the data presented, and therefore also with the conclusions and recommendations given.

The authors show that the risk of leprosy being diagnosed in household contacts is highest in those households in which the index case had a positive skin smear at diagnosis.  They therefore recommend that skin smear services need to be revived, so that contact tracing can focus on those households with the highest risk.

When looking at the data presented in Table 2 of the paper, however, it is clear that 405 (67%) of the 608 new cases found amongst contacts were from households in which the index cases were smear negative.  Although the relative risk is higher for contacts in households with a smear positive index case (presented as a hazard ratio of 1.57 per level of increase in skin smear positivity in the multivariate analysis), screening contacts in households with smear-negative index cases will identify many more patients in absolute terms, because there are many more smear negative index cases.  In addition, it is often the case that when examining the contacts of a PB case, the "real index case", an undiagnosed MB case, is found among their contacts.

Leprosy is a relatively rare disease and covering all leprosy affected households with contact screening is certainly feasible. Various studies even point to the value of expanding the range of contacts beyond the household level (4 - 6). It therefore seems counter-productive to focus our attention on reviving skin smear services, in order to try and save money by limiting contact examinations to a much smaller pool – the households of smear positive index cases – thereby neglecting the much larger pool of other contacts, in the household and beyond. The skin smear is a useful test for other reasons, so it is unfortunate that the authors have pitched two good interventions against each other.

Privacy is certainly an issue when planning a program of contact examination; alternative methods such as skin camps or focal surveys should be considered when the level of stigma means that individual index cases do not wish to be publically identified.

Contact examination is currently the most efficient method of active case-finding available to leprosy programs. Whether or not it is combined with some form of post-exposure prophylaxis, it remains important and worthwhile to examine as large a group of contacts as is feasible.

Paul Saunderson, Member of the ILEP Technical Commission, Editor-in-Chief of Leprosy Review

Peter Steinmann, Epidemiologist, Swiss Tropical and Public Health Institute

Epco Hasker, Epidemiologist, Institute of Tropical Medicine, Antwerp, Belgium

Liesbeth Mieras, Head of the Technical Department, NLR until No Leprosy Remains

Mauricio LIsboa Nobre, Leprologist and Dermatologist, Giselda Trigueiro Hospital (Brazil); Member of GPZL Leadership Team 

References

1. Quilter EEV, Butlin CR, Singh S, et al. Patients with skin smear positive leprosy in Bangladesh are the main risk factor for leprosy development: 21-year follow-up in the household contact study (COCOA). PLoS Negl Trop Dis. 2020; 14(10): e0008687.  doi.org/10.1371/journal.pntd.0008687

2. Butlin CR, Nicholls P, Bowers B, et al. Household examinations: outcome of routine surveillance of cohorts in Bangladesh. Lepr Rev. 2019; 90 (3): 290–304.

3. Butlin CR, Nicholls P, Bowers B, et al. Outcome of late healthy household contact examinations in leprosy-affected households in Bangladesh. Lepr Rev. 2019; 90 (3): 305–320.

4. Singh RK, Singh A, Marella S, et al. Case finding through contact surveys and focal surveys in Bihar, India. Lepr Rev. 2016; 89 (3): 436-7.

5. Ortuno-Gutierrez N, Baco A, Braet S, et al. Clustering of leprosy beyond the household level in a highly endemic setting on the Comoros, an observational study. BMC Infectious Diseases. 2019; 19:501.  doi.org/10.1186/s12879-019-4116-y

6. Moura ML, Dupnik KM, Sampaio GAA, et al. Active surveillance of Hansen's Disease (leprosy): importance for case finding among extra-domiciliary contacts. PLoS Negl Trop Dis. 2013; 7(3): p. e2093.

LML - S Deepak, B Naafs, S Noto and P Schreuder

LML blog link: http://leprosymailinglist.blogspot.it/

Contact: Dr Pieter Schreuder << editorlml@gmail.com

--
You received this message because you are subscribed to the Google Groups "Leprosy Mailing List" group.
To unsubscribe from this group and stop receiving emails from it, send an email to leprosymailinglist+unsubscribe@googlegroups.com.
To view this discussion on the web, visit https://groups.google.com/d/msgid/leprosymailinglist/770ffc25-49da-4887-882a-e06b2e5814a5n%40googlegroups.com.