Sociodemographic characteristics of the study Subjects
Out of the 1,316 subjects enrolled in the study, 71 were excluded (52 did not produce urine samples and 19 failed to return their questionnaires) giving a response rate of 94.6%. The recruited children were from 16 primary and 4 secondary schools in rural-Ogo-Oluwa and 8 primary and 5 secondary schools in urban-Ogbomoso South LGA. Six hundred and fifty-five (52.7%) of the 1,245 subjects were recruited from the rural settings. The mean age of the study population was 10.6 ± 3.0 years. Five hundred and forty-seven (43.9%) were males.
Results of dipstick urinalysis in study subjects screened for proteinuria
Of the 1,245 subjects who had dipstick urinalysis, only 10 had significant proteinuria giving a proportional prevalence of 0.8% (95% CI: 0.4%-1.5%).Age adjusted prevalence rate was 0.8% (95% CI: 0.4%-1.5%) using the 2006 census population standard. The peak age prevalence of dipstick proteinuria (Figure 2) was at age 12 years [4/160 (2.5%)]. Fifty-eight subjects (4.7%) had leucocyturia while 18(1.4%) tested positive for haematuria. Nitrite was positive in one subject.
Age-specific prevalence of proteinuria among 1245 subjects
Using spot urine protein-creatinine, 224 children had a ratio of ≥ 0.2, placing the crude prevalence of proteinuria at 224/1245 (18.0%; 95% CI: 15.9- 20.2%). The age-adjusted prevalence rate was 20.3% (95% CI: 18.1 - 22.6%) using 2006 census results as population standard. The prevalence of proteinuria had double peak, first at age group 5 year; 23/80-(28.8%) and thereafter at age 15-year 23/96 (24.0%). The prevalence of significant proteinuria reached its nadir at age nine-year 8/80 (10.0%) as shown in Figure 2.
Gender-specific prevalence of proteinuria
Of the 224 subjects with significant proteinuria by UPr/UCr ratio, 140 out of 698 (20.1%) were females while 84 out of 547 (15.4%) were males (p=0.032).Out of the ten subjects with significant proteinuria by dipstick urinalysis, 2/10 (20.0%) were females while 8 of the 10 (80.0%) were males (p=0.026).
Proportion of subjects with nephrotic range proteinuria
Ten (0.8%) of 1,245 had nephrotic range proteinuria giving a crude prevalence of 0.8% (95% CI: 0.4% – 1.5%) by the two methods of assessing for proteinuria. Of these methods, spot UPr/UCr ratio identified 9/10 (90%) while 3/10 (30%) were detected by dipstick method.
Agreement between methods of testing proteinuria
The paired analysis (UPr/UCr and Dipstick) with McNemar test showed a statistically significant difference in the proportion of proteinuria detected by the methods (McNemar; p < 0.001) as shown in Table I. The biserial correlation coefficient was low (r= 0.092; p=0.001).Seven of the ten subjects with significant dipstick urinalysis proteinuria were negative for significant UPr/UCr ratio. The odds for spot urine protein creatinine ratio to detect proteinuria was two times more than the dipstick method. Cohen’s Kappa coefficient showed very poor agreement (Kappa = 0.01; 95% CI: -0.015 - 0.036).
Of the 224 subjects with significant proteinuria who were followed up for significant proteinuria, only 118 (52.64%) were accessible for further evaluation. One hundred and sixty-two (72.3%) belong to the lower social class. Estimated glomerular filtration rate (eGFR) was 92.81 ± 16.82 ml/min/1.73m2 and 53 (44.5%) had eGFR of less < 90 ml/min/1.73m2. Eight (6.8%) of the subjects were found to have Schistosoma haematobium and were treated with praziquantel. One (0.8%) had E coli urinary tract infection and received antibiotics. Five (4.2%) subjects were hepatitis BsAg positive while two (1.7%) of the students tested positive to Anti HCV. Three (2.5%) of the participants tested positive to HIV rapid diagnostic test, they were further evaluated and enrolled on treatment. Six (5.1%) subjects had haemoglobinopathy on haemoglobin electrophoresis (three with haemoglobin SS, one haemoglobin CC & one haemoglobin SC) and were referred to Paediatric Haematology clinic for further follow up. Seven (5.9%) of the 118 subjects had elevated blood pressure (pre-hypertension), and 4 (3.4%) had hypertension. The four with hypertension are follow up at Paediatric Nephrology Clinic. Five (4.2%) subjects had renal abnormalities on ultrasonography with two having grade II renal parenchymal disease.