Family Practice Vol. 21, No. 1, 18-21
© Oxford University Press 2004, all rights reserved.
Article |
The value of urine screening in a young adult population
Departments of a Nephrology and b Radiology, Leicester General Hospital, and c Freemen's Common Health Centre, Leicester, UK
Correspondence to Dr Peter S Topham, Department of Nephrology, University Hospitals of Leicester NHS Trust, Leicester General Hospital, Gwendolen Road, Leicester LE5 4PW, UK; E-mail: Peter.Topham{at}uhl-tr.nhs.uk
Received 9 October 2002; Revised 8 August 2003; Accepted 8 September 2003.
Topham PS, Jethwa A, Watkins M, Rees Y and Feehally J. The value of urine screening in a young adult population. Family Practice 2004; 21: 18–21.
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Abstract |
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Background. GPs in England and Wales are required to perform screening urinalysis on all newly registered patients. The value of this practice, however, is unclear.
Objective. The purpose of this study was to identify the prevalence of persistent urine abnormalities and to establish the added value of screening for both haematuria and proteinuria in a large cohort of young adults in the UK.
Methods. Urine screening was carried out in a cohort of young adults in a student health centre and a university hospital nephrology unit in a large British city. University students enrolling for health screening in a university health centre over a 2-year period were tested for haematuria and/or proteinuria by dipstick urinalysis. Subjects with persistent urine abnormalities were evaluated for the presence of significant renal tract pathology.
Results. Of 3808 students screened, 3570 provided an initial urine sample; 220 were abnormal. Of these, 38 (1% of original cohort) had persistent abnormalities (haematuria, 14; proteinuria, 16; both, eight). Subjects with isolated haematuria or proteinuria did not have significant pathology. In contrast, all the students with both haematuria and proteinuria had identifiable renal disease.
Conclusions. Our findings do not support the value of routine screening for proteinuria or haematuria in young adults. However, the combination of haematuria and proteinuria is a powerful predictor for parenchymal renal disease. Thus, if proteinuria is detected, further testing for haematuria should be performed.
Keywords. Glomerular disease, haematuria, proteinuria, screening, urinalysis.
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Introduction |
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Although urinalysis for proteinuria and haematuria is a basic tool in the investigation of renal tract disease,1 the role of population-wide urine screening remains contentious.2 Nonetheless, GPs in the UK are required to perform urine testing for glucose and protein on those who newly register with a practice [NHS (General Medical Services) Regulations 1990, para. 14]. The justification for urine screening remains questionable2 given the relative rarity of renal disease and the lack of specific therapy.
Existing data on screening focus on those aged over 35 years.3 There are few data regarding the value of urine screening in younger populations.4–6 Thus, the aim of the study was to identify the prevalence and significance of urine abnormalities in a large cohort of young adults in the UK.
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Methods |
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Setting
The Freemen's Common Health Centre is a student health service that registers 1900 new students each academic year. Leicester General Hospital is a university hospital providing specialist services in nephrology.
Screening protocol
The study was approved by the Leicestershire Ethics Committee. At the time of registering with the practice, all students were invited for a health check, which included a urine dipstick test for blood, protein and glucose. Positive results prompted a request for two further urine samples. If the students failed to provide the additional urine samples, two further reminder letters were sent.
Urine was tested using Haema-combistix (provided by Dr RG Newall, Bayer, UK).
Two further specimens were requested from patients with an initial positive reading (>1+) for blood and/or protein and, if also dipstick positive, urine was sent for bacteriological culture. Exclusion of infection prompted further assessment in the nephrology department at Leicester General Hospital.
Proteinuria
Orthostatic proteinuria was not an indication for renal biopsy. Students with persistent proteinuria >0.5 g/24 h with normal renal imaging were offered a renal biopsy.
Haematuria
Students with dipstick-positive haematuria (>1+ on at least two out of three specimens) in the absence of urinary sepsis, menstruation or strenuous exercise were offered a renal biopsy and flexible cystourethroscopy.
Haematuria and proteinuria
Patients with persistent microscopic haematuria and proteinuria (>0.15 g/24 h) were offered a renal biopsy.
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Results |
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Urine screening (Fig. 1)
During 1996 and 1997, 3808 students attended for screening (52% female, mean age 21.8 years, range 18–59 years). A total of 238 (6.3%) provided no specimen despite two reminders. Two hundred and twenty of the remaining 3570 (6.2%) had a positive test for blood or protein [135 proteinuria (3.8%), 62 haematuria (1.7%), 23 proteinuria and haematuria (0.6%)]. No glycosuria was detected. Of the 220 with a positive test, 40 had a positive second test (two urinary sepsis, both female), 132 had no subsequent abnormality and 48 provided no further sample despite three reminder letters. Thus, 38 students (1%) had persistent proteinuria and/or haematuria [16 (0.45%) persistent proteinuria, 14 (0.39%) persistent haematuria and eight (0.23%) persistent proteinuria and haematuria] and were referred for nephrological evaluation.
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Persistent proteinuria (Fig. 1)
Persistent proteinuria was identified in 16 individuals (13 females, three males). Six failed to attend for follow-up investigation despite three written reminders. Ten patients were seen in the nephrology clinic. One had orthostatic proteinuria, one had a congenital single kidney, and one patient (0.6 g/24 h) declined renal biopsy. Seven patients with protein excretion between 0.15 and 0.3 g/24 h were not offered renal biopsy, but annual surveillance was suggested.
Persistent microscopic haematuria (Fig. 1)
Fourteen individuals had persistent microscopic haematuria (11 females, three males).
Seven were incompletely investigated: three failed to attend for GP consultation despite three reminder letters, and four left the UK.
Six patients were seen in the nephrology clinic: one had an upper pole renal scar; two patients declined renal biopsy; and three patients underwent renal biopsy that was normal in all cases. Cystourethroscopy was arranged for all patients, but none attended. The remaining patient had active Hodgkin's disease and investigation was deferred.
Persistent proteinuria and haematuria (Fig. 1)
Persistent proteinuria and haematuria was found in eight individuals (seven female, one male). Three patients had previously diagnosed renal disease: one chronic renal insufficiency, one renal transplant, and one lupus nephritis.
Two patients presented with symptomatic renal disease during the screening process: one with acute interstitial nephritis and the other with lupus nephritis.
Three patients were found to have previously unrecognized renal disease: one presumed familial renal disease (declined renal biopsy) and two thin membrane nephropathy on renal biopsy.
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Discussion |
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Any health screening programme is justified by its capacity to identify patients with significant treatable disease using a technique which is acceptable to the general population, has high specificity and sensitivity and is cost effective. Although screening for proteinuria and glycosuria is a requirement in the standing instructions for General Medical Services in the UK, the value of such screening has been questioned.2
In this selected university student study population, the prevalence of proteinuria of 0.45% accords well with other studies of this age group.4 We wished to identify those with persistent non-orthostatic proteinuria since intermittent and orthostatic proteinuria is benign.7 However, all subjects had <1 g/24 h proteinuria, which is unlikely to represent significant renal disease, although regular monitoring is warranted.
In younger age groups (<30 years), the prevalence of persistent isolated microscopic haematuria is reported to be <2%.4,8 We found 1.7% with a single positive test and 0.39% with persistent haematuria.
Since malignancy is very rare in young adults, the purpose of screening is to identify renal stones, structural renal tract abnormalities or parenchymal renal disease. In our study, all three of the patients who underwent renal biopsy for isolated persistent haematuria had normal renal histology. Other renal biopsy studies indicate that at least 50% of young adults will have identifiable glomerular disease on renal biopsy, most commonly IgA nephropathy and thin membrane nephropathy.9 However, many British nephrologists consider that establishing a diagnosis with a biopsy may not be justified10 given the extremely low risk of progressive renal disease and the lack of specific therapy. In a cohort of 478 patients, none progressed to chronic renal failure (CRF) in a mean follow-up period of 5 years, although 10.6% developed proteinuria during follow-up.8
The prevalence of persistent haematuria and proteinuria is <1% in all age groups.8 We found only eight cases (0.23%). Nonetheless, the combination of haematuria and proteinuria is a powerful predictor of significant parenchymal disease. In one study, 14.9% developed CRF over a mean 5.8 year follow-up.8 In this study, the only patients identified with renal disease of immediate significance had haematuria and proteinuria. However, only three of the eight patients with renal disease were detected as a direct result of the screening process.
Thus, our findings do not support routine screening for proteinuria or haematuria in this particular young adult population given the low diagnostic yield. However, a positive dipstick test for proteinuria should prompt a further test for haematuria.
Finally, the data we present here also highlight some of the difficulties associated with screening programmes: 6% provided no urine specimen despite a well co-ordinated recall system; 22% of those with an initial abnormal result provided no further specimen; and 34% of those with persistent urine abnormality defaulted during evaluation.
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References |
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1 Cameron JS. The patient with proteinuria and/or haematuria. In Davison AM, Cameron JS, Grunfeld J-P, Kerr DNS, Ritz E, Winearls CG (eds). Oxford Textbook of Clinical Nephrology. Oxford: Oxford University Press; 1998: 441–459.
2 Mant D, Fowler G. Urine analysis for glucose and protein: are the requirements of the new contract sensible? Br Med J 1990; 300: 1053–1055.
3 Britton JP, Dowell AC, Whelan P, Harris CM. A community study of bladder cancer screening by the detection of occult urinary bleeding. J Urol 1992; 148: 788–790.[Web of Science][Medline]
4 Kawamura T, Ohta T, Ohno Y et al. Significance of urinalysis for subsequent kidney and urinary tract disorders in mass screening of adults. Intern Med 1995; 34: 475–480.[Medline]
5 Froom P, Ribak J, Benbassat J. Significance of microhematuria in young adults. Br Med J 1984; 288: 20–22.
6 Levitt JI. The prognostic significance of proteinuria in young college students. Ann Intern Med 1967; 66: 685–696.
7 Rytand DA, Spreiter S. Prognosis in postural (orthostatic proteinuria). Forty to fifty-year follow-up of six patients after diagnosis by Thomas Addis. N Engl J Med 1981; 305: 618–621.[Web of Science][Medline]
8 Yamagata K, Kobayashi M, Koyama A. A long-term follow up study of asymptomatic hematuria and/or proteinuria in adults. Clin Nephrol 1996; 45: 281–288.[Web of Science][Medline]
9 Topham PS, Harper SJ, Furness PN, Harris KPG, Walls J, Feehally J. Glomerular disease as a cause of isolated microscopic haematuria. Q J Med. 1994; 87: 329–335.[Web of Science][Medline]
10 Feehally J, O'Donoghue DJ, Ballardie FW. Current nephrological practice in the evaluation of haematuria: relationship to the incidence of IgA nephropathy. J R Coll Physicians Lond 1989; 23: 228–231.[Web of Science][Medline]
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