DIAGNOSTIC PERFORMANCE OF SALIVARY UREA NITROGEN IN SCREENING FOR KIDNEY DISEASE AND ITS ROLE IN ASSESSING SEVERITY OF KIDNEY DYSFUNCTION IN DIABETICS WITH OR WITHOUT HYPERTENSION

Introduction:

Kidney disease, both acute and chronic, is highly prevalent worldwide with an average prevalence of 13.4 % of adult population, constituting about 850 million people and leads to preventable deaths. Early detection is the key to prevent progression to end stage kidney failure. Early stages of kidney diseases are usually without much symptoms. Hence the importance of screening for kidney diseases in the high risk individuals. Currently urine albumin creatinine ratio and serum creatinine are the two recommended screening test for chronic kidney disease, but it requires laboratory backing, refrigerated storage of reagents and electricity. This impedes their use in the poorest and most rural areas in the developing countries. Diagnosis of kidney disease in these settings, therefore, remains a significant challenge. Salivary urea nitrogen, as measured by dipstick, has been formerly shown to be parallel to the convectional markers of renal disease like serum creatinine, eGFR and has been effective in diagnosing kidney disease and furthermore in monitoring response to treatment. This non-invasive diagnostic test with minimal risk and skill to provide a dependable assessment of disease condition would be of worth to both the health care system and the patients. 

Methods:

OBJECTIVES : 1. To estimate Salivary urea nitrogen in diabetic patients with or without hypertension, with normal renal function and patients with varying stages of CKD with albuminuria. 2. To correlate salivary urea nitrogen level with conventional marker of renal function – serum creatinine, blood urea nitrogen, eGFR in the above patients. 3. To determine whether salivary urea can be used as screening marker for kidney disease.

METHODS: A cross sectional prospective was conducted in Yenepoya Medical College Hospital Mangalore, involving 96 participants who were diabetics with or without hypertension were enrolled. Salivary urea nitrogen of all participants were measured using the SUN dipsticks. Urine protein, urine ACR, serum creatinine, blood urea and eGFR of all participant were measured. Diagnostic performance of the presenting SUN dipstick to detect kidney disease were calculated by area under the ROC curve, and cut-off values can be established. The sensitivity and specificity of SUN was calculated.

Results:

SUN levels were assessed in diabetic patients with or without hypertension, with normal renal functions and varying stages of renal dysfunction. SUN showed a statistically significant positive correlation with urine ACR with p-value of 0.014. SUN showed statistically significant positive correlation with urine RBC with p-value of 0.001. SUN also demonstrated a statistically significant positive correlation with serum creatinine and blood urea, and a negative correlation with eGFR. The spearman’s rho correlation showed the SUN had statistically significant correlation with all conventional markers of renal dysfunction like serum creatinine, blood urea and eGFR. Among these variables SUN had highest association with blood urea with Spearman’rho correlation coefficient being 0.863 and followed by serum creatinine with correlation coefficient of 0.760. We also found that ROC curve of SUN in patients with moderately increased albuminuria and eGFR of more than 60ml/min/1.73m² had a AUC of 0.725 with an optimal cut off at level 3 of SUN(25-34mg/dl) and a sensitivity of 52% and sensitivity of 86%, which was statistically significant with p-value of 0.001. The ROC curve of SUN with decreasing level of eGFR was showing an increasing AUC, maximum in eGFR of less than 15ml/min/1.73m² with AUC of 0.954 with an optimal cut off at level 4 of SUN (35-54mg/dl) and a sensitivity of 100% and specificity of 84.9%, which was statistically significant with p-value of 0.001.

Conclusions:

In our study we found that Salivary Urea Nitrogen correlates with the conventional markers of renal dysfunction like the serum creatinine, blood urea, eGFR and albuminuria. SUN was able to detect kidney dysfunction in patients with moderately increased albuminuria and eGFR of more than 60ml/min/1.73m², thus proving itself as an useful screening tool in early diagnosis of renal dysfunction in diabetic patients and also to assess the severity of renal dysfunction in them.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.