Leprosy Mailing List – December 5, 2015
Ref.: (LML) Leprosy and mainstream scientific definitions
From: Joel Almeida, Mumbai and London
Dear Pieter,
A.Trend in the incidence rate of leprosy in India
With increasing delay in diagnosis,
- The number of new cases detected decreases (owing to self-healing); but
- The proportion of new cases with visible deformity increases.
Therefore standardising the number of new cases detected by the proportion (or %) with visible deformity at diagnosis averts an important error.
The Table shows that the standardised number of new cases in India is increasing with time. Claims that the incidence rate of leprosy is declining, in India, seem contrary to the evidence. The trend is positive, not negative.
Trend in incidence rate of leprosy in India, 2008-9 to 2014-15 | ||||
Time (years) | a. New cases detected** | b. No. with visible deformities at diagnosis** | c. % with visible deformities at diagnosis** | d. Standardised number of new cases* |
2008-9 | 134000 | 3752 | 2.80 | 108718 |
2009-10 | 134000 | 4154 | 3.10 | 120366 |
2010-11 | 127000 | 3927 | 3.09 | 113788 |
2011-12 | 127000 | 3865 | 3.04 | 111992 |
2012-13 | 135000 | 4650 | 3.44 | 134738 |
2013-14 | 127000 | 5256 | 4.14 | 152297 |
2014-15 | 125785 | 5794 | 4.61 | 167886 |
| total | total | average | total |
| 909785 | 31398 | 3.451 | 909785 |
*In each year, d = a x c / (average of c)
**source: Indian leprosy programme (NLEP) reports
d, the standardised number of new cases, is increasing over time (test for non-zero slope, p<0.01).
B. Definition of elimination
"Elimination" is defined by the second WHO NTD report (2013) as "the reduction to zero of the incidence of infection caused by a specific pathogen in a defined geographical area as a result of deliberate efforts."
Other usages of the term "elimination" are not only scientifically incorrect, but also open the door to damaging complacency. This complacency opens the door to needless nerve damage and disfigurement among tens of thousands of leprosy patients in India each year.
C. "Burden" of leprosy: definition
"Burden of disease" has a very specific meaning in the scientific community. It has a clear unit of measurement for non-fatal conditions: YLD (years lived with disability).
YLD is defined as "the prevalence of each sequela multiplied by the relevant disability weight adjusted for comorbidity." (Murray et al, GBD 2010: design, definitions, and metrics (comment). The Lancet Vol 380 December 15/22/29, 2012, pages 2063-2066).
Other usages of the term "burden" gratuitously place leprosy patients at a disadvantage relative to those afflicted by other diseases. Such erroneous usage of "burden" also encourages premature elimination of leprosy patients from the registers. This premature elimination of patients from registers gratuitously exposes them to nerve damage and disfigurement.
No reasonable scientist could imagine that the transmission of M. leprae is reduced merely by discharging patients from registers.
D. Implications for leprosy control
Definitions consistent with the mainstream of science would greatly benefit leprosy patients and populations at risk of leprosy. This will happen: the sooner the better. It would be good if we, the leprosy fraternity, hasten that day.
Regards,
Joel Almeida
LML - S Deepak, B Naafs, S Noto and P Schreuder
LML blog link: http://leprosymailinglist.blogspot.it/
Contact: Dr Pieter Schreuder << editorlml@gmail.com
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