The prevalence of CKD is increasing, and the condition is becoming a global public health problem. Taiwan is one of countries with high prevalence of CKD. The national prevalence of CKD was estimated to be 11.93 %, and only 3.54 % of patients in Taiwan with CKD were aware of their disorder (Wen et al. 2008). If not diagnosed early and well controlled, CKD might progress into end-stage renal disease (ESRD). Patients with ESRD usually received kidney transplantation or hemodialysis therapy, both of which cost disproportionate amounts in healthcare resources and impaired the quality of life of patients. According to the report of the National Health Insurance Administration, Ministry of Health and Welfare, Taiwan, in 2008, approximately 56,000 people (0.24 % of all people covered by the National Health Insurance) underwent regular dialysis treatment and expended 11 % of the annual healthcare reimbursement. Therefore, it is important for healthy individuals to receive periodic urine screening to prevent the development of incident CKD.
The method for screening for significant proteinuria has not been clearly defined and regulated in Taiwan. The relatively new method of protein detection on a urine dipstick incorporating urine creatinine estimation has been demonstrated to be a more sensitive indicator for detecting significant proteinuria (Xin et al. 2004; Price et al. 2005; Wang et al. 2009; Methven et al. 2010). Distinct from the conventional dipstick test, the semi-quantitative urine P/C ratio possessed an additional advantage for the correction of urine concentration variation by detecting urine creatinine level and, therefore, increased the screening rate of diluted urine samples. In our institution, the abnormal or diluted results of semi-quantitative urine P/C ratio testing for urine samples sent to the laboratory were further interpreted and commented by the clinical pathologist, and were subsequently validated in real time in the outpatient clinic or in the ward. However, the traditional dipstick test remains the most common method used by clinical laboratories for detecting significant proteinuria. As a result, physicians should correlate the clinical manifestations of patients with the urinalysis report carefully because significant proteinuria might be missed because of diluted or underestimated urine samples in such situations. Therefore, it is necessary that the efficacy of each laboratory methods for detecting proteinuria should be compared and analyzed. To the best of our knowledge, our study is the first to describe the underestimated report of urine protein examination for the semi-quantitative P/C ratio, traditional dipstick and quantitative urine protein methods.
The benefits of routine screening for CKD remain controversial, in spite of the increasing prevalence of CKD. Previously, it was suggested that there was no cost-effectiveness of early detection of urine protein for retarding the progression and decreasing the mortality of CKD, unless the urine protein examination was selectively directed toward high-risk groups such as elderly and hypertensive subjects (Boulware et al. 2003). Otherwise, urine protein examinations were recommended to be conducted at an intermission of approximately 10 years in the healthy adult population (Boulware et al. 2003). However, a recent study revealed that universal screening for proteinuria appeared to be an effective strategy for reducing the CKD population because a high positive rate of proteinuria in the general population was shown in Asians, even in persons without hypertension or diabetes (Yamagata et al. 2008). In view of this fact, a more sensitive urine screening tool for proteinuria is necessary, especially for Asian subjects. Besides, the average costs of the quantitative and semi-quantitative urine P/C ratio for a single test in our institution were 2.58 and 2.42 US dollars, respectively. It seems that use of the semi-quantitative urine P/C ratio testing could lead to a minor decrease in cost compared to that of the gold standard testing. The semi-quantitative urine P/C ratio might be a good choice for early detection of proteinuria and appeared to be more effective than the traditional dipstick urine protein test, particularly in diluted urine aliquots.
It is important for physicians to screen for and diagnose CKD based on rapid and accurate urine examinations. Therefore, patients are required to be available for re-collection of urine aliquots for repeated urinalysis, consuming unnecessary laboratory and time costs for further testing confirmation. Considering these factors, patients should be well educated to not consume too much water before urine sample collection because normal or diluted results of the semi-quantitative urine P/C ratio would be present, and falsely negative results could be reported. If this factor is taken into consideration, unnecessary urinalysis retests could be avoided, and timely management could be initiated as needed.
There are some limitations in the present study. First, it was unknown whether subjects undergoing urine protein screening had any underlying diseases such as hypertension or diabetes. Moreover, information regarding racial differences, family history and personal medication use were not available. Additionally, the age of the subjects for proteinuria screening was not included in the exclusion criteria in our study, resulting in some extent of selection bias.
To summarize, the present study indicated that the urine P/C ratio evaluated by a semi-quantitative method is clinically applicable based on its better sensitivity and screening ability for significant proteinuria than other laboratory methods, particularly in diluted urine samples. To establish an effective strategy for CKD prevention in the Asian populations, urine protein screening with semi-quantitative P/C ratio could be considered.
