Productivity Loss Related to Neglected Tropical Diseases Eligible for Preventive Chemotherapy: A Systematic Literature Review

Background
Neglected Tropical Diseases (NTDs) not only cause health and life expectancy loss, but can also lead to economic consequences including reduced ability to work. This article describes a systematic literature review of the effect on the economic productivity of individuals affected by one of the five worldwide most prevalent NTDs: lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminths (ascariasis, trichuriasis, and hookworm infection) and trachoma. These diseases are eligible to preventive chemotherapy (PCT).
Methodology/Principal Findings
Eleven bibliographic databases were searched using different names of all NTDs and various keywords relating to productivity. Additional references were identified through reference lists from relevant papers. Of the 5316 unique publications found in the database searches, thirteen papers were identified for lymphatic filariasis, ten for onchocerciasis, eleven for schistosomiasis, six for soil-transmitted helminths and three for trachoma. Besides the scarcity in publications reporting the degree of productivity loss, this review revealed large variation in the estimated productivity loss related to these NTDs.
Conclusions
It is clear that productivity is affected by NTDs, although the actual impact depends on the type and severity of the NTD as well as on the context where the disease occurs. The largest impact on productivity loss of individuals affected by one of these diseases seems to be due to blindness from onchocerciasis and severe schistosomiasis manifestations; productivity loss due to trachoma-related blindness has never been studied directly. However, productivity loss at an individual level might differ from productivity loss at a population level because of differences in the prevalence of NTDs. Variation in estimated productivity loss between and within diseases is caused by differences in research methods and setting. Publications should provide enough information to enable readers to assess the quality and relevance of the study for their purposes.

背景
被忽视的热带病（Neglected Tropical Diseases, NTDs）不仅会造成健康损害与预期寿命损失，还会引发包括劳动能力下降在内的一系列经济后果。本文针对全球五大流行最为广泛的被忽视热带病——淋巴丝虫病（lymphatic filariasis）、盘尾丝虫病（onchocerciasis）、血吸虫病（schistosomiasis）、土源性蠕虫病（soil-transmitted helminths，涵盖蛔虫病、鞭虫病与钩虫感染）以及沙眼（trachoma）——对患者个体经济生产力的影响，开展了一项系统文献综述。上述疾病均可采用预防性化学治疗（preventive chemotherapy, PCT）。

方法论/主要研究结果
本研究检索了11个书目数据库，检索词覆盖所有被忽视热带病的不同称谓以及与生产力相关的各类关键词；同时通过检索相关文献的参考文献列表补充获取了额外参考文献。在数据库检索获得的5316篇独立文献中，针对淋巴丝虫病的有13篇、盘尾丝虫病10篇、血吸虫病11篇、土源性蠕虫病6篇、沙眼3篇。本综述发现，除了报道生产力损失程度的文献较为匮乏之外，与上述被忽视热带病相关的估算生产力损失也存在显著差异。

结论
显而易见，被忽视热带病会对生产力造成影响，但其实际影响程度取决于该类疾病的类型、严重程度以及疾病发生的具体场景。此类疾病患者的生产力损失中，受影响最显著的似乎是盘尾丝虫病所致失明以及重症血吸虫病表现；而沙眼相关性失明导致的生产力损失尚未有直接研究报道。不过由于被忽视热带病的流行率存在差异，个体层面的生产力损失与群体层面的生产力损失可能并不一致。不同疾病之间以及同一疾病内部的估算生产力损失差异，源于研究方法与研究场景的不同。相关研究文献应提供充足信息，以便读者能够依据自身需求评估该研究的质量与相关性。