Flow cytometry of urinary erythrocytes for evaluating the source of haematuria

Non-nephronal hematuria misdiagnosed as C1q nephropathy: Look before you leap

A 19-year-old male presented with persistent macroscopic hematuria for last 3 months. On initial evaluation, he was found to have minimal proteinuria, normal renal function, and normal complement with negative lupus serology. Light microscopy, immunofluorescence and electron microscopy of renal tissue confirmed the presence of C1q nephropathy. Because of poor response to immunosuppressive agent (prednisolone and mycophenolate mofetil), passage of urinary clot once and vexing persistent macroscopic hematuria, alternative diagnosis was considered. Cystourethroscopy showed urethritis of prostatic urethra. Immunosuppressives were stopped and doxycycline started to which hematuria responded dramatically. This case report illustrates that hematuria in this patient was because of undiagnosed urethritis rather than incidental C1q nephropathy.

Assessment of haematuria: automated urine flowmetry vs microscopy

BACKGROUND

Microscopy of the urine sediment may be a useful method in the distinction between a glomerular and a non-glomerular source of urinary bleeding. However, microscopic techniques are time consuming and hampered by inter-observer variations. In the present study we have therefore compared bright-field microscopy with automated urine flowmetry (Sysmex UF-100), examining their ability to differentiate between glomerular and non-glomerular haematuria.

METHODS

Fresh urine samples were obtained from 112 patients with a well-defined, single cause of a positive dipstick test. Their urine specimens were examined within 4 h in a blinded manner. Of them, 79 specimens had a positive dipstick for blood and thus could be evaluated for haematuria.

RESULTS

The Sysmex UF-100 had a sensitivity and specificity of 0.83 and 0.94 respectively in detecting non-glomerular bleeding. The positive and negative predictive values were 0.95 and 0.78 respectively. The corresponding values of microscopy were 0.79 and 0.90 respectively, and 0.93 and 0.74 respectively.

CONCLUSIONS

Automated flowmetry can be used in the distinction between glomerular and non-glomerular haematuria.

A new automated system for urine analysis: a simple, cost-effective and reliable method for distinguishing between glomerular and nonglomerular sources of haematuria

OBJECTIVE

To determine the ability, reliability and accuracy of a new automated system of urine analysis in differentiating glomerular from nonglomerular bleeding in the initial investigation of haematuria, and compare its efficacy with conventional phase-contrast microscopy (PCM).

PATIENTS AND METHODS

One hundred and six urine samples from patients in whom the final diagnosis was available were analysed using electrical flow impedance to detect, enumerate and size red blood cells in a conductive fluid (the cellfacts analyser, Microbial Systems Ltd, Coventry, UK). All the samples were also tested using a dipstick method and PCM was carried out for comparison on 45 of the 106 urine specimens. The results of cellfacts analysis were correlated with the final diagnoses to assess sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of this method; the costs were also analysed.

RESULTS

Sixty-nine urine samples tested positive for blood on dipstick urine analysis and all these were confirmed to have red blood cells on cellfacts analysis. The remaining 37 samples were negative for blood on dipstick testing and cellfacts analysis, although seven patients had been referred with previously detected microscopic haematuria, none of whom were found to have any detectable pathology in the urinary tract on clinical examination and investigations. The remaining 30 patients were diagnosed to have urological or nephrological conditions with no haematuria. In the positive group, 20 (29%) patients were from the glomerular group, with a mean (range) red blood cell size of 4.25 (4-5.1) micrometer, and 49 (71%) from the nonglomerular group, with red blood cells of 5.47 (4.67-5.70) micrometer. These ranges overlapped at 4.67-5.1 micrometer at the decision threshold of 4.75 micrometer, the distribution of dysmorphic and eumorphic red blood cells for the glomerular group was 18 (90%) and two (10%), respectively, and for the nonglomerular group was 2 (4%) and 47 (96%), respectively. The sensitivity, specificity, PPV and NPV were 90%, 96%, 90% and 96%, respectively. Consumable and labour costs were very low.

CONCLUSIONS

Cellfacts analysis is a simple, rapid, objective and cost-effective method for differentiating glomerular from nonglomerular urinary red blood cells, especially when few such cells are present.

The value of comparative volumetric analysis of urinary and blood erythrocytes to localize the source of hematuria

PURPOSE

We evaluate comparative volumetric analysis of blood and urinary red blood cells (RBCs) to identify the source of hematuria. Comparative volumetric analysis is defined as the difference between mean corpuscular erythrocyte volume in peripheral blood (MCVB) diluted in urine supernatant after centrifugation and mean corpuscular volume of urinary erythrocytes (MCVU). The potential of MCVB-MCVU to distinguish the origin of hematuria is compared to MCVU alone. The fundamental hypothesis is that RBCs that can go through the glomerulus will be smaller than those from the collecting system or lower urinary tract, thus having a smaller MCVU and larger difference between MCVB and MCVU.

MATERIALS AND METHODS

A prospective detailed urological evaluation was performed on 210 patients with glomerular or nonglomerular hematuria detected by urinary sediment, clinical radiological evaluation, endoscopy, cytology and sometimes bladder or renal biopsy. After evaluation 24 cases with an uncertain source of hematuria were excluded from study. Specialized urinalysis, volumetric analysis and clinical investigation were performed in a blind fashion. MCVU and MCVB-MCVU were registered for every patient. The Technicon H-3 system with angle laser scattering dual system allowed measurement of mean corpuscular volume in a minimal number of RBCs, and resuspension of RBC pellets in the same urinary supinate avoided effects of osmolarity and pH on RBC size and shape. Reproducibility in assessing the index was tested in 50 cases in which comparative volumetric analysis was repeated on 2 consecutive days. Unpaired t test was performed, and a threshold value of MCVB-MCVU with maximum sensitivity and specificity to detect glomerular hematuria was identified. The potential of urinary and comparative volumetric analysis to distinguish the source of hematuria was evaluated and compared by receiver operating characteristics curve analysis.

RESULTS

Hematuria was nonglomerular in 53 (28.4%) and glomerular in 133 (71.6%) patients. Mean MCVB-MCVU was significantly different for nonglomerular (0.6 fl.) and glomerular (30.5 fl.) sources (p<0.0001). There was a correlation between repeat independent measures of MCVU and MCVB-MCVU. The highest positive predictive value to detect a glomerular origin is desirable so that unnecessary investigation can be obviated without the risk of missing a nonglomerular source. With a limit of 16 fl. specificity and positive predictive value were 98 and 99%, respectively. Receiver operating characteristics curve analysis to localize the source of hematuria revealed significant differences in favor of comparative volumetric analysis versus urinary volumetric analysis alone.

CONCLUSIONS

MCVB-MCVU using the Technicon H-3 system is a useful noninvasive and accurate method to locate the source of hematuria. A value of 16 fl. or greater practically rules out a nonglomerular origin and obviates further urological investigation. We have incorporated this investigation in our diagnostic algorithm for hematuria.