Aim: The gold standard for the determination of proteinuria, an independent risk factor for cardiovascular and renal disease, is the measurement of protein in a 24-hour urine collection. However, this method has been shown to be unreliable mainly due to poor compliance of sampling by patients. This study investigates other appropriate means of predicting 24-hour urinary protein excretion in a sample of Afro-Caribbeans in Barbados by assessing the correlation of actual and estimated urinary protein excretion between a 24-hour urine collection sample, 12-hour (AM and PM) and spot (AM and PM) urine collections.
Subjects and Method: A convenient sample of 30 healthy participants of Afro-Caribbean origin between the ages of 21 and 55 years was recruited for the study. The 24-hour urine samples and anthropometric data were collected as documented in the study’s standard clinical procedure. A 24-hour urine sample was collected as two separate 12-hour AM and PM samples. In addition, two spot samples (AM and PM) were taken during each 12-hour sample collection period. Analysis of the urinary protein and creatinine was done with a Roche/Hitachi Modular System (Roche Diagnostics, IN, USA). SPSS version 19 was used to analyse the data to make inferences.
Results: Thirty Afro-Caribbean persons participated in the study: 16 females and 14 males. The average age and body mass index (BMI) were 38 ± 17 years and 25.32 ± 5.98 kg/m2, respectively. The Spearman Rho’s correlation was used to interpret associations of the urinary parameters in 24-hour collected sample and the other samples. The strongest correlation of the protein:creatinine ratio in the 24-hour collected sample to the other samples was observed with the 12-hour AM sample (r = + 0.743, p < 0.01) followed by the 12-hour PM sample (r = +0.672, p < 0.01). On analysing gender, the more significant correlations found were among the males for the 12-hour timed samples with r = +0.945, p < 0.01 and r = +0.736, p < 0.01 for the AM and PM samples, respectively. There were very strong correlations between the 24-hour urinary protein excretion and the estimated 24-hour protein excretion from the 12-hour AM and PM samples (r = +0.846, p < 0.01 and r = +0.637, p < 0.01, respectively).
Both males and females had the strongest correlation for the estimation of 24-hour protein excretion in the 12-hour AM sample (r = +0.795, p < 0.01 and r = +0.965, p < 0.01, respectively).
Conclusion: The use of a 12-hour timed sample, specifically the morning sample, may be a more convenient way to assess proteinuria in the Afro-Caribbean population. This method allows for a quicker assessment of proteinuria which not only allows earlier diagnosis of renal disease but may also reduce the clinical cost of the disease’s management.