Consistency of Refrigerated Pathological Urine Sediment

Abstract

Urinalysis is a routine medical laboratory investigation, as examination of the urine plays a vital role in the diagnosis of kidney diseases. Sometimes the identification of urine sediment needs confirmation by expertise in clinical microscopy, and this is difficult in the far rural area in the developing countries. Here, the author evaluated a feasibility to use refrigerated urine sediment for repeated analysis. In this work, the author found that it is feasible to use refrigerated urine sediment for repeated analysis. The good correlation (> 0.9) can be seen for the epithelium, red blood cell, and cast but not for the white blood cell. The consistency of the repeat analysis results are an orderly decrease from epithelium (4 days), red blood cell (3 days), white blood cell (3 days), and cast (2 days). However, as time passes, reliability decreases.

Keywords:

• urine sediment
• refrigerate
• analysis

INTRODUCTION

Urinalysis is a routine medical laboratory investigation, as examination of the urine plays a vital role in the diagnosis of kidney diseases.[1],[2] Routine urine chemical indices, calculation of the fractional excretion of sodium, and examination of the urine sediment are valuable in characterizing the cause of renal failure.[1] The findings of casts and blood cells in the urine provide valuable clues about the causes of the underlying renal pathology.[2] In addition, disease progression can also be determined by urine sediment analysis.[3]

However, a limitation in urinalysis is that a freshly collected specimen is required. Generally, the urinalysis should be performed within half an hour after urine collection.[4] Sometimes, the identification of urine sediment needs confirmation by expertise in clinical microscopy, and this is difficult in far rural areas in developing countries. Although the urine preservation can be applied, the reagent is usually unavailable in the laboratory of community hospital. Here, the author evaluated the feasibility to use refrigerated urine sediment for repeated analysis.

MATERIALS AND METHODS

This study was designed as a laboratory-based study. The authors collected remainder urine samples from routine analysis at the laboratory of King Chulalongkorn Memorial Hospital, Bangkok, Thailand, for this study. Thirty urine samples from the patients with the pathological urine sediments indicating renal diseases are recruited. All urine samples were sent to the laboratory on the same period and were centrifuged and prepared for urine sediment according to the standard urinalysis protocol. The urine sediment was investigated under light microscope according to the urinalysis protocol and then kept in the refrigerator at 4°C. Repeated analyses were performed every day on the same period continuously for five days. The studied urine sediment parameters included white blood cell, red blood cell, epithelium, and cast.

All laboratory analyses in the study were performed by an experienced medical technologist in clinical microscopy. The laboratory was accredited by ISO15189 standards. The data from urine sediment analysis were collected and analyzed by descriptive statistical analysis. Correlations among the resulted urine sediment parameters analyzed in different days were calculated. SPSS 6.0 for Windows was used for all statistical analysis in this work, and a p value < 0.05 was accepted as a statistically significant level.

RESULTS

Correlations among white blood cell, red blood cell, epithelium, and cast analyzed in different days were presented in 1–4, respectively.

Table 1 Correlations among white blood cell analyzed in different days

Days	0	1	2	3	4
0	1	0.734	0.733	0.451	0.349
1	0.734	1	0.960	0.996	0.932
2	0.733	0.960	1	0.910	0.801
3	0.451	0.996	0.910	1	0.768
4	0.349	0.932	0.801	0.768	1

*Correlation is significant at the level 0.05 level.

Table 2 Correlations among red blood cell in different days

Days	0	1	2	3	4
0	1	0.979	0.863	0.814	0.442
1	0.979	1	0.984	0.996	0.952
2	0.863	0.984	1	0.949	0.754
3	0.814	0.996	0.949	1	0.883
4	0.442	0.952	0.754	0.883	1

*Correlation is significant at the level 0.05 level.

Table 3 Correlations among epithelium analyzed in different days

Days	0	1	2	3	4
0	1	0.989	0.934	0.955	0.932
1	0.989	1	0.985	0.979	0.924
2	0.934	0.985	1	0.975	0.786
3	0.955	0.979	0.975	1	0.912
4	0.932	0.924	0.786	0.912	1

*Correlation is significant at the level 0.05 level.

Table 4 Correlations among cast analyzed in different days

Days	0	1	2	3	4
0	1	0.981	0.624	0.307	0.284
1	0.981	1	0.783	0.607	0.581
2	0.624	0.783	1	0.512	0.482
3	0.307	0.607	0.512	1	0.407
4	0.284	0.581	0.482	0.407	1

*Correlation is significant at the level 0.05 level.

DISCUSSION

Renal failure is defined in general terms as an abrupt decrease in renal function sufficient to result in the retention of nitrogenous waste and disrupt fluid and electrolyte homeostasis.[1] In laboratory medicine, cells and casts of urinary sediment can be used to predict the prognosis of patients with renal disease.[5] Indeed, urinalysis is a simple, efficient, and accurate guide in the diagnosis of renal disease.[6] Gay et al. said that the mechanism of renal failure could be determined by urine sediment examination in most cases, sometimes allowing to rectify a previous diagnosis.[7] They also noted that the value of this examination seemed to be more of anatomoclinical than of prognostic interest, mainly for definite or polyfactorial renal dysfunctions.[7]

In this work, the author found that it is feasible to use refrigerated urine sediment for repeated analysis. The good correlation (> 0.9) can be seen for epithelium, red blood cell, and cast, but not for white blood cell. Of the three parameters with good correlation, the consistency of the repeat analysis results in an orderly decrease of epithelium (4 days), red blood cell (3 days), and cast (2 days). However, as time passes, reliability decreases. The authors recommend that the refrigerated urine sediment could be used for repeated analysis in the process of consultation; however, it should be used within 1–2 days.