Measuring morbidity in schistosomiasis mansoni: relationship between image pattern, portal vein diameter and portal branch thickness in large-scale surveys using new WHO coding guidelines for ultrasound in schistosomiasis.
OBJECTIVE
World Health Organization consensus meetings on 'Ultrasound in Schistosomiasis' in 1996 and 1997 anticipated further challenges in the global implementation of a standardized protocol for morbidity assessment in schistosomiasis mansoni. We evaluated the performance of the qualitative and quantitative components of the new Niamey criteria.


METHODS
Use of the Niamey protocol among 3954 subjects in two linked, cross-sectional ultrasound surveys of Schistosoma mansoni-endemic populations in Egypt and Kenya.


RESULTS
There were significant differences between Egyptian and Kenyan sites in prevalence and age distribution of S. mansoni-related hepatic fibrosis (36%vs. 3%, P < 0.001). Protocol image pattern scoring could be performed quickly and was stable to interobserver variation. However, there were unintended but systematic differences between study sites in the measurement of portal vein diameter (PVD) and wall thickness. By Niamey criteria, a high prevalence of portal dilation was scored for normal Egyptian subjects, which reduced the predictive value of image pattern for portal hypertension. Using alternative height-indexing of PVD, image pattern plus PVD findings predicted 15% of Egyptians and 2.5% of Kenyans were at risk for variceal bleeding, whereas locally derived PVD norms estimated 25% of Egyptians and 12% of Kenyans to be at possible risk.


CONCLUSIONS
Niamey scoring criteria performed acceptably as a relative grading system for disease in schistosomiasis mansoni, but failed to account fully for site-to-site variation in test performance and morbidity prevalence. Consequently, standardized image pattern scoring appears to provide the most useful tool for detection and comparison of S. mansoni-associated morbidity in large-scale surveys.
King
Charles H
CH
Division of Geographic Medicine, Case Western Reserve University and University Hospitals of Cleveland, OH 44103-4983, USA. chk@po.cwru.edu
Magak
Philip
P
Salam
Ekram Abdel
EA
Ouma
John H
JH
Kariuki
H Curtis
HC
Blanton
Ronald E
RE
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D003430:Cross-Sectional Studies; D004108:Dilatation, Pathologic / Q000000981:diagnostic imaging / Q000469:parasitology; D004534:Egypt / Q000453:epidemiology; D004932:Esophageal and Gastric Varices / Q000469:parasitology / Q000473:pathology; D005260:Female; D006471:Gastrointestinal Hemorrhage / Q000469:parasitology / Q000473:pathology; D006801:Humans; D006975:Hypertension, Portal / Q000469:parasitology / Q000473:pathology; D007630:Kenya / Q000453:epidemiology; D008103:Liver Cirrhosis / Q000000981:diagnostic imaging / Q000469:parasitology; D008109:Liver Diseases, Parasitic / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D011169:Portal Vein / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D015995:Prevalence; D012044:Regression Analysis; D012307:Risk Factors; D012423:Rural Health; D012555:Schistosomiasis mansoni / Q000000981:diagnostic imaging* / Q000453:epidemiology; D014463:Ultrasonography