Urinary microscopy as seen by nephrologists

Pitfalls in the diagnosis of hematuria

Detection of hemoglobin (Hb) and red blood cells in urine (hematuria) is characterized by a large number of pitfalls. Clinicians and laboratory specialists must be aware of these pitfalls since they often lead to medical overconsumption or incorrect diagnosis. Pre-analytical issues (use of vacuum tubes or urine tubes containing preservatives) can affect test results. In routine clinical laboratories, hematuria can be assayed using either chemical (test strips) or particle-counting techniques. In cases of doubtful results, Munchausen syndrome or adulteration of the urine specimen should be excluded. Pigmenturia (caused by the presence of dyes, urinary metabolites such as porphyrins and homogentisic acid, and certain drugs in the urine) can be easily confused with hematuria. The peroxidase activity (test strip) can be positively affected by the presence of non-Hb peroxidases (e.g. myoglobin, semen peroxidases, bacterial, and vegetable peroxidases). Urinary pH, haptoglobin concentration, and urine osmolality may affect specific peroxidase activity. The implementation of expert systems may be helpful in detecting preanalytical and analytical errors in the assessment of hematuria. Correcting for dilution using osmolality, density, or conductivity may be useful for heavily concentrated or diluted urine samples.

Comparison of the diagnostic performance of two automated urine sediment analyzers with manual phase-contrast microscopy

Background

Recently, several manufacturers have launched automated urinalysis platforms. This study aimed to compare the diagnostic performance of the UF-5000 (Sysmex Corporation, Kobe, Japan) and the cobas® u 701 (Roche Diagnostics, Rotkreuz, Switzerland) urine sediment analyzers with manual phase-contrast microscopy as the reference method.

Methods

A total of 195 urine samples were analyzed on both automated platforms and subjected to manual microscopic examination. Agreement was assessed by Cohen’s kappa (κ) analysis. Sensitivities and specificities were calculated.

Results

The agreement of the UF-5000 with manual microscopy was almost perfect (κ > 0.8) for red (RBC) and white blood cells (WBC), renal tubular epithel cells, hyaline casts, bacteria (BACT) and yeast (YLC), substantial (κ = 0.61–0.80) for squamous epithel cells (SEC) and pathologic casts, and moderate (κ = 0.41–0.60) for transitional epithel cells. The cobas® u 701 showed substantial agreement (κ = 0.61–0.80) for WBC, moderate agreement (κ = 0.41–0.60) for hyaline casts, and fair agreement (κ = 0.21–0.40) for RBC, SEC, non-squamous epithel (NEC), pathologic casts, BACT and YLC. The UF-5000 sensitivities ranged between 98.5% for RBC and 83.3% for pathological casts. The cobas® u 701 showed sensitivities between 83.0% for WBC and 31.6% for YLC.

Conclusions

The UF-5000 (Sysmex) analyzer showed a better diagnostic agreement with manual phase-contrast microscopy compared to the cobas® u 701 (Roche) module. The Sysmex platform showed reliable results for urine sediment analysis. However, pathological samples should be verified with manual microscopy.

The urine sediment as a biomarker of kidney disease

The modern era of medicine has ushered in new diagnostic technologies to assist the clinician in evaluating patients with kidney disease. The birth of automated urine analysis technology and centralized laboratory testing has unfortunately made examination of urine sediment by physicians a rare event. At the same time, identifying novel urine biomarkers for kidney disease has become a research priority in nephrology, and the search for the "renal troponin" has progressed at a fast pace. Despite this, urine sediment examination remains a time-honored test that provides a wealth of information about the patient's kidney condition and performs favorably as a urinary biomarker. It alerts the clinician to the presence of kidney disease and provides diagnostic information that often identifies the compartment of kidney injury. In addition, sediment findings may guide therapy and assist in prognostication. As such, it is premature to abandon urine sediment examination. It may be more appropriate to combine urine sediment examination with new candidate biomarkers that enter clinical practice to create a "diagnostic panel" that provides clinicians with a useful battery of diagnostic tests. To accomplish this, we as nephrologists must encourage continued training and maintenance of competency in urine sediment examination.

Clinical Use and Pathogenetic Basis of Laboratory Tests for the Evaluation of Primary Arterial Hypertension

This review focuses on the laboratory biochemical tests that are useful in the diagnostic approach to the hypertensive patient. A "minimal" diagnostic laboratory work-up, including a small number of tests that are simple and relatively inexpensive, is first described. Because these tests provide basic information on the presence of major cardiovascular (CV) risk factors and target organ damage, and might give some clues to the presence of a secondary form of hypertension (HT), they should be performed on all patients presenting with HT. Other tests that are aimed at assessing the overall CV risk, a major determinant of prognosis that dictates the therapeutic strategy in the individual HT patient, are then discussed. They allow identification of major CV risk factors and associated clinical conditions which, if present, lead to a substantial change of therapeutic strategy. The role of C-reactive protein as a marker of atherosclerosis and its predictive value for CV events are also discussed. Finally, a section is devoted to tests that are currently confined to research purposes, such as markers of endothelial function including endothelin-1, homocysteine and genetic analysis.

Prediction of diagnosis of immunoglobulin A nephropathy prior to renal biopsy and correlation with urinary sediment findings and prognostic grading

Several clinical markers correlate well with the diagnosis and prognosis of IgA nephropathy (IgAN). In the present study, we re-evaluated the usefulness of these four clinical markers for prediction of the diagnosis of patients with IgAN through a comparison between many more patients with IgAN and those with other types of renal diseases. 364 patients with IgAN and 289 with other types of renal disease were examined. An analysis was performed prior to renal biopsy, using clinical markers including, serum IgA, serum IgA/C3 ratio, number of red blood cells in urinary sediments, and urinary protein. Patients with IgAN were divided into four groups according to histopathological findings. Presence of microscopic hematuria, persistent proteinuria, high serum IgA levels, and the serum IgA/C3 ratios are useful for prediction of diagnosis of IgAN and distinguishing it from other renal diseases. Blood pressure, urinary protein, serum uric acid, renal function, and urinary sediment findings may be useful for prediction of prognostic grading in patients with IgAN.

Advances in the clinical laboratory assessment of urinary sediment

Urinalysis has been used extensively in clinical practice to aid in the diagnosis of various renal and urologic diseases. The innovation of urinalysis is marching on right along with the rapid developments in biotechnology and astride from the solo urine cytology to sophisticated studies of individual component in the urinary sediment. In this review article, we focus on the use of flow cytometry and other technical advances in the examination of urinary sediment, the detection of urologic malignancies by the presence of microsatellite alteration in the urinary sediment, as well as the quantification of cytokine messenger RNA (mRNA) expression in urinary sediment by reverse transcription and real-time quantitative polymerase chain reaction (RT-QPCR). Notably, the study of cytokine mRNA expression in urinary sediment by RT-QPCR has recently been reported to provide important diagnostic information in kidney allograft recipients and patients with lupus nephritis. This simple and non-invasive method requires further study to determine its role in risk stratification and monitoring of therapeutic response in patients with other kidney diseases.

The clinical art and science of urine microscopy

PURPOSE OF REVIEW

The examination of urine sediment is a diagnostic test which is frequently neglected by nephrologists. With this review the authors wanted to demonstrate that it can provide useful and relevant information in a wide spectrum of clinical situations.

RECENT FINDINGS

The authors reviewed the main contributions dealing with urine sediment examination, published in international journals in the period from January 2002 to April 2003. After a section on methodological aspects, they described the importance of urine sediment examination in various diseases of the urinary tract. These included bladder B-lymphoma, systemic histoplasmosis, urate nephropathy, Fabry disease, myeloma cast nephropathy, giant cell arteritis, and lupus nephritis. The significance of 'decoy cells' in the urine as a marker of polyomavirus BK reactivation was also discussed, both in renal transplantation and other conditions such as solitary pancreas transplantation, chronic lymphatic leukaemia, and HIV infection. In the section devoted to urine sediment changes caused by drugs the authors dealt with leukocyturia induced by indinavir, and crystalluria, which can follow amoxycillin and acyclovir administration. Finally, they reported on the utility and limits of flow cytometry for the automated analysis of urine sediments.

SUMMARY

The review of the recent literature on urine sediment examination shows that this test has important clinical implications in a large spectrum of diseases. Therefore, it should be more widely used by nephrologists.