Normal values of aortic root diameters in sub-Saharan Africans: The TAHES study

Abstract Introduction Reference values of aortic root diameters (ARD) are proposed to define normal versus diseased aorta. However, reported ranges of normal values are mostly issued from Caucasian cohorts. Data on blacks African subjects are sparse and not issued from community-dwelling cohorts. Purpose Our study aimed to establish reference values for ARD in a Beninese general population cohort. Methods This study is a part of TAHES, a population-based prospective cohort study initiated in 2015 in the district of Tanvè, Republic of Benin. Demographic, blood pressure and blood glucose data were collected using a questionnaire adapted from WHO-STEPS tools. Transthoracic echocardiography examinations were performed by 4 cardiologists, and analyzed off-line by a single observer. ARD were measured using inner-edge to inner-edge diameters during diastole for sinuses of Vasalva (SV), sinotubular junction (STJ) and proximal ascending aorta (AA), and during systole for annulus. Normal limits were defined as the 95th percentiles. Variables are presented as mean ±SD (5th-95th percentiles). Results We included 513 normotensive, non-diabetic and cardiovascular disease-free individuals (206 men and 307 women, age 40±14 years [26–68]). The absolute values of ARD were significantly greater in men: the non-indexed ARD values for the annulus, SV, STJ and AA were respectively 21.3±2 (18.5–25), 28.5±3.4 (23–34), 24.1±3 (19–29) and 27±3 (22.5–32) mm for men and 19.3±1.8 (1.8 (15- 22), 25.8±2.8 (21.6–30), 22±2.7 (18–26) and 24.8±2.8 (21–30) mm for women, respectively (all p<0.0001). No significant differences between sexes were recorded for body surface area (BSA)-indexed ARD for Annulus, STJ and AA. BSA-indexed SV dimension was greater in men (17.3±2.6 mm; 13.5–22) than women (16.8±2.5 mm; 13–21). There was a correlation between SV, STJ, AA indexed-diameters and age in both sexes but not for annulus indexed-diameter (r=0.14, 0.19 and 0.36 for women and 0.34, 0.45 and 0.32 for men, all p<0.05). The upper limits for ARD are summarized in Table 1. In order to compare these values to those in Caucasians, the data of the NORRE study are also displayed. Conclusion Normal values from a general population in West Africa appear could to differ from those established in Caucasian populations. This ethnic-appropriate reference is proposed for appropriate diagnosis in patients in sub-Saharan Africa. FUNDunding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): APREL (CHU Limoges) Table 1

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Establishing Cutoffs for Streptococcal Antibody Titers in Uganda: Implications for Rheumatic Fever Diagnosis

10.1101/19010447 ◽

2019 ◽

Author(s):

Emmy Okello ◽

Meghna Murali ◽

Joselyn Rwebembera ◽

Jenifer Atala ◽

Nada Harik ◽

...

Keyword(s):

Heart Disease ◽

Rheumatic Fever ◽

Rheumatic Heart Disease ◽

Normal Values ◽

Sub Saharan Africa ◽

Age Group ◽

Upper Limit ◽

Antibody Titers ◽

Sub Saharan ◽

Rheumatic Heart

AbstractBackgroundCentral to rheumatic fever (RF) diagnosis is evidence of streptococcal exposure, specifically antistreptolysin O (ASO) and antideoxyribonuclease B (ADB) antibodies. It is unknown if these antibody titers should be adjusted to the background exposure rates of GAS or if published standards should be used. Here, we establish the normal values of ASO and ADB in Uganda and examine RF case detection using published vs. population-specific thresholds.MethodsParticipants (age 0-50 years) were recruited. ASO was measured in-country by nephelometric technique. ADB samples were sent to Australia (PathWest) for ADB determination by enzyme inhibition assay, andthe 80% upper limit values by age were established. The published standard values for ASO (200IU/ml) and ADB (375IU/ml) were compared to the Ugandan 80% upper limit of normal values (ULN) for RF case detection in children 5-15 years.FindingsOf the 428 participants, 16 were excluded from analysis (9 sore throat, 1 skin sores, 5 fever, 4 echocardiograms showing occult RHD), and 183 of the remaining were children 5-15 years. The median ASO titer in this age group was 220 IU/ml, with the 80th percentile value of 389 IU/ml. The median ADB titer in this age group was 375 IU/ml, with the 80th percentile value of 568 IU/ml. Application of new Ugandan cutoffs to 528 children enrolled in our prospective RF study, reduced the number of definite RF cases to 120/528 (22·7%), as compared to 173/528 (32·8%) using published normal values.InterpretationThe 80th percentile ULN for ASO and ADB are higher in Uganda than in other countries. Applying these higher values to RF diagnosis in Uganda results in higher diagnostic specificity, but some unknown loss in sensitivity. Implications of over-diagnosis and missed cases will be explored through a longitudinal follow-up study of children in the RF research program.FundingThis work was supported by American Heart Association Grant #17SFRN33670607 / Andrea Beaton / 2017 and DELTAS Africa Initiative.Research in contextEvidence before this studyWe searched PubMed for data on normal values of streptococcal antibody titers within diverse populations between database inception and January 1, 2019, using the search terms (rheumatic fever) OR (streptococcal antibodies). Nine studies were identified, but only one was from sub-Saharan Africa (2018, Ethiopia) and it was limited by vague exclusion criteria and lack of data on anti-DNase B. Given the high burden of rheumatic heart disease in sub-Saharan Africa, further data is needed to determine normal streptococcal antibody titers in this population and to assess the clinical impact of different cutoffs for RF diagnosis.Added value of this studyOur study utilized a rigorous approach to exclude patients with history of recent possible streptococcal exposure including skin and throat infection and employed echocardiography to exclude patients with pre-existing rheumatic heart disease. Additionally, this study was conducted in parallel to a larger epidemiological cohort study of rheumatic fever in Uganda, allowing us, for the first time, to prospectively determine how utilization of different streptococcal antibody titer cutoffs affect diagnosis of rheumatic fever.Implications of all the available evidenceRheumatic fever remains a challenging diagnosis based on a clinical decision rule with imperfect sensitivity and specificity. Improved understanding of streptococcal antibody titers in rheumatic heart disease endemic populations may improve diagnostic performance. Our study also points to the need for development of a rheumatic fever diagnostic test, in order to provide a more definitive assessment of risk.

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