(LML) Number and proportion of PB Leprosy cases reported in the annual WER reports 1985- 2017

Leprosy Mailing List – April 4,  2019

Ref.:   (LML)  Number and proportion of PB Leprosy cases reported in the annual WER reports 1985- 2017

From:  Ruth Butlin, Bangladesh and Diana Lockwood, London, UK

---

Dear Pieter,

We have looked at the Weekly Epidemiological Record (WER) over the last 34 years to establish the numbers of leprosy cases treated and their classification. Since 1985, we calculate that world-wide, at least 15,253,582 new cases have been diagnosed and treated with multi drug therapy (MDT). This includes 5,753,753 cases allocated to Multibacillary (MB) regimen.  Another 9,499,829 new leprosy cases have been diagnosed as Paucibacillary (PB) leprosy and treated with MDT (table 1), according to data extracted from reports in the Weekly Epidemiological Records of respective years (refs 1-20). This includes a few who were treated with rifampicin, ofloxacin and minocycline in the single dose regimen for "single lesion leprosy". The vast majority would have been prescribed dual therapy (Rifampicin and dapsone) for 6 months.

Although the Weekly Epidemiological Record's Global leprosy situation articles usually contain the previous year's figures for all new cases reported and for all new MB cases, there has not been a consistent format used since 1985, and in some years new case figures were not disaggregated by leprosy group. There are also limitations to the data presented, since the staff at WHO are dependent on concerned countries submitting full & accurate information. The number of countries reporting each year has varied. In most years no data was given for Europe. These issues have been highlighted by others (ref Fine, 2008, 21, and de Clercq 2012, 22). Occasionally the total new case detection figure published has been revised in the following year, as more reports were received late. If the revised total did not include the MB/PB proportions, it was not utilised in this paper.

In the WER, data on treatment completion rates are very scanty, so have been ignored. Apparently, the cure rate for both MB and PB cases treated with WHO-recommended MDT is high although there is a paucity of good quality studies following up cohorts of MDT-treated PB cases over a long period to establish the true relapse rate.

There is a remarkable shift in the proportion of PB cases amongst new cases, from nearly 80% in early years to 40% since 2012. The question is: does this shift represent a real epidemiological change or is it entirely artefactual, or multi-factorial?

An artefactual change could be due to different operational guidelines in use at different periods, or due to bias based on the quality of classification skills amongst those (predominantly field workers) who decide whether the new case is PB or MB. Their decisions in turn often rest on the availability and quality of skin smear services.

We reviewed the guidelines on allocation to PB or MB groups. When the concept of PB/MB was first introduced (ref.23) allocation criteria were the patient's Madrid classification or Ridley Jopling classification, and a case whose skin smear was 1+ could be considered as PB. After a few years, it was advised to include all smear positive cases in the MB group (ref. 24), which should decrease the proportion of new cases who were allocated to the PB regimen.

In 1998, the recommended method of grouping was changed to skin lesion counting (ref. 25) The expert committee suggested the following: paucibacillary single lesion leprosy (one skin lesion); paucibacillary leprosy (2-5 skin lesions); multibacillary leprosy (more than 5 skin lesions). Later "single lesion PB" cases were included with other PB cases, defined as having 5 or less skin lesions (ref 4), with the proviso that if skin smear was positive the case should be given MB regimen. One might have expected that these criteria would decrease the PB proportion since many BT cases had multiple lesions. On the other hand, failure to use skin smear services (or, poor quality smear reading with many false negatives) might have meant that some BL cases were mistakenly put into the PB group, because they had few skin lesions. It is also possible that, as skin smear services declined, many early LL cases (with diffuse infiltration but no distinct patches) might have been missed when suspects were examined in peripheral clinics. That would similarly have had the effect of increasing the proportion of PB amongst actually-diagnosed new cases (relative underdiagnosis of MB cases).

The skin lesion count system for classification is still recommended (ref. 26 and ref. 27). However, in several authoritative publications it is stated that if there is doubt about allocating patients to PB or to MB groups, MB regimen should be used (ref 28, also refs 25,27), and perhaps this advice has been widely taken. Field workers lacking confidence in their classification skills might over-use the MB regimen thinking it will be safer to over-treat PB cases than to risk under-treating MB cases. This could explain a marked decrease in PB proportion, such as we have seen.

The fact that the decline is gradual, not step-wise in line with timing of changes to guidelines, would suggest it is either a true epidemiological phenomenon, or a slowly progressive change in behaviour of health workers. If the reported change is not due to a "real" epidemiological change over time, it could mean there has been excessive expense (to programmes) and undue medication-burden for thousands of leprosy cases who received MB MDT instead of the more-appropriate PB regimen.

We would be most interested to hear the views of others on this question, in particular if anyone has evidence from epidemiological studies (or from an audit of any large leprosy control project) relating to it.

C Ruth Butlin,

formerly overseas staff of The Leprosy Mission International, currently honorary Medical Adviser to DBLM Hospital and Rural Health Programmes of TLMI Bangladesh.

Diana Lockwood,

Professor of Tropical Medicine, London School of Hygiene and Tropical Medicine.

Table 1

year	All new cases	MB new cases	PB new cases		PB%
19851	550224	113551	436673	79.36%
1986	573790	119080	454710	79.25%
1987	595145	131294	463851	77.94%
1988	553597	119267	434330	78.46%
1989	550743	123187	427556	77.63%
1990	571792	151622	420170	73.48%
1991	613016	189679	423337	69.06%
1992	667133	225416	441717	66.21%
1993	615830	215640	400190	64.98%
19942	560646	195161	365485	65.19%
1995	529376	185017	344359	65.05%
1996	566567	154729	411838	72.69%
1997	684961	239120	445841	65.09%
19983	804357	321743	482614	(60%)
1999	738112	295245	442867	(60%)
2000	719330	280539	438791	61.00%
2001	763262	305305	457957	(60%)
2002	620638	248255	372383	(60%)
2003	514718	205887	308831	(60%)
2004	407791	194372	213419	52.34%
2005	299036	158728	140308	46.92%
2006	259017	137409	121608	46.95%
2007	254525	140174	114351	44.93%
2008	249007	140392	108615	43.62%
2009	244796	139125	105671	43.17%
2010	228474	125559	102915	45.04%
2011	219075	125513	93562	42.71%
2012	232857	137410	95447	40.99%
2013	215656	129464	86192	39.97%
2014	213899	126091	87808	41.05%
2015	210758	126783	83975	39.84%
2016	214783	127013	87770	40.86%
2017	210671	125983	84688	40.20%
total	15253582	5753753	9499829	62.28%

Notes

1. 1985-1993 data is for only highest-burden 32 countries
2. 1994-1999, PB% from 32 countries applied to all new cases
3. 1998, 1999, 2001, 2002, 2003, PB cases estimated at 60% all new cases

References

1. WHO.Leprosy situation in the world in 1997, Weekly epidemiological record 1997 vol 72 no 39 pages 293-296
2. WHO. Elimination of leprosy as a public health problem (update), Weekly epidemiological record 1998 vol 73 no 40 pages 305-312
3. WHO. Leprosy - Global situation, Weekly epidemiological record 2000 vol 75 no 28 pages 225-232
4. WHO. Leprosy - Global situation, Weekly epidemiological record 2000 vol 75 no 34 page 280 (correction)
5. WHO. Leprosy, Weekly epidemiological record 2001 vol 76 no 23 pages 173-180
6. WHO. Leprosy, Weekly epidemiological record 2002 vol 77 no 1 pages 1-8
7. WHO. Global leprosy situation 2005, Weekly epidemiological record 2005 vol 80 no 34 pages 289-296
8. WHO. Global leprosy situation 2006, Weekly epidemiological record 2006 vol 81 no 32 pages 309-316
9. WHO. Global leprosy situation 2007, Weekly epidemiological record 2007 vol 82  no 25 pages 225-232
10. WHO. Global leprosy situation, beginning 2008. Weekly epidemiological record 2008 vol 83 no 33 pages 293-300
11. WHO. Global leprosy situation 2009, Weekly epidemiological record 2009 vol 84 no 33 pages 333-340
12. WHO. Global leprosy situation 2010, Weekly epidemiological record 2010 vol 85 no 35 pages 337-348
13. WHO. Leprosy update 2011, Weekly epidemiological record 2011 vol 86 no 36 pages 389-400
14. WHO. Global leprosy situation 2012, Weekly epidemiological record 2012 vol 87 no 34 pages 317-328
15. WHO. Global leprosy -Update on the 2012 situation, Weekly epidemiological record 2013 vol 88. No 35 pages 365-380
16. WHO. Global leprosy update, 2013; reducing disease burden, Weekly epidemiological record 2014 vol 89 no 36 pages 389-400
17. WHO.  Global leprosy update, 2014: need for early case detection, Weekly epidemiological record 2015 vol 90 no 36 pages 461-476
18. WHO.  Global leprosy update, 2015: time for action, accountability and inclusion, Weekly epidemiological record 2016 vol 91 no 35 pages 405-420
19. WHO.  Global leprosy update, 2016: accelerating reduction of disease burden, Weekly epidemiological record 2017 vol 92 no 35 pages 501-520
20. WHO.  Global leprosy update, 2017: reducing the disease burden due to leprosy. Weekly epidemiological record 2018 vol 93 no 35 pages 444-456
21. Fine PEM, 2008, Leprosy's global statistics- still room for improvement. Leprosy Review 2008, 79, 235-238.
22. deClercq E, 2012, Leprosy figures: no time for self-complacency. Leprosy Review 2012, 83, 3-5.

23. WHO 1982 Chemotherapy of leprosy for control programmes: report of a WHO study group. Geneva, World Health Organization, 1982. (WHO Technical Report Series, No.   675).

24. WHO  1988. WHO Expert Committee on leprosy: sixth report. (WHO technical report series; no. 768)

25. WHO 1998. WHO Expert Committee on leprosy: seventh report. (WHO technical report series; no. 874)

26.WHO. 2009 Enhanced Global Strategy for Further Reducing the Disease Burden Due to Leprosy. Operational Guidelines (Updated). SEA-GLP-2009.4 publ. WHO SEARO 2009

27. WHO 2012. WHO Expert Committee on leprosy: eighth report. (WHO technical report series; no. 968)

28. WHO 1994 Chemotherapy of leprosy: report of a WHO study group. Geneva, World Health Organization, 1994. (WHO Technical Report Series, No. 847).

---

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

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

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