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Validating the prediction of lower urinary tract infection in primary care: sensitivity and specificity of urinary dipsticks and clinical scores in women

Validating the prediction of lower urinary tract infection in primary care: sensitivity and specificity of urinary dipsticks and clinical scores in women
Validating the prediction of lower urinary tract infection in primary care: sensitivity and specificity of urinary dipsticks and clinical scores in women
Background: Dipsticks are one of the most commonly used near-patient tests in primary care, but few clinical or dipstick algorithms have been rigorously developed.

Aim: To confirm whether previously documented clinical and dipstick variables and algorithms predict laboratory diagnosis of urinary tract infection (UTI).

Design of study: Validation study.

Setting: Primary care.

Method: A total of 434 adult females with suspected lower UTI had bacteriuria assessed using the European Urinalysis Guidelines.

Results: Sixty-six per cent of patients had confirmed UTI. The predictive values of nitrite, leucocyte esterase (+ or greater), and blood (haemolysed trace or greater) were confirmed (independent multivariate odds ratios = 5.6, 3.5, and 2.1 respectively). The previously developed dipstick rule — based on presence of nitrite, or both leucocytes and blood — was moderately sensitive (75%) but less specific (66%; positive predictive value [PPV] 81%, negative predictive value [NPV] 57%). Predictive values were improved by varying the cut-off point: NPV was 76% for all three dipstick results being negative; the PPV was 92% for having nitrite and either blood or leucocyte esterase. Urine offensive smell was not found to be predictive in this sample; for a clinical score using the remaining three predictive clinical features (urine cloudiness, dysuria, and nocturia), NPV was 67% for none of the features, and PPV was 82% for three features.

Conclusion: A clinical score is of limited value in increasing diagnostic precision. Dipstick results can modestly improve diagnostic precision but poorly rule out infection. Clinicians need strategies to take account of poor NPVs.
algorithms, clinical scoring, diagnosis, urinary tract infection, primary care, urinalysis
0960-1643
495 -500
Little, P.
1bf2d1f7-200c-47a5-ab16-fe5a8756a777
Turner, S.
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Rumsby, K.
a9d758fb-5246-4c27-b8ad-c4fb72576aea
Jones, R.
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Warner, G.
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Moore, M.
1be81dad-7120-45f0-bbed-f3b0cc0cfe99
Lowes, J.A.
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Smith, H.
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Hawke, C.
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Leydon, G.
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Mullee, M.
fd3f91c3-5e95-4f56-8d73-260824eeb362
Little, P.
1bf2d1f7-200c-47a5-ab16-fe5a8756a777
Turner, S.
42f19397-8e9f-435d-a348-2cc1639b5eb4
Rumsby, K.
a9d758fb-5246-4c27-b8ad-c4fb72576aea
Jones, R.
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Warner, G.
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Moore, M.
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Lowes, J.A.
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Smith, H.
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Hawke, C.
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Leydon, G.
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Mullee, M.
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Little, P., Turner, S., Rumsby, K., Jones, R., Warner, G., Moore, M., Lowes, J.A., Smith, H., Hawke, C., Leydon, G. and Mullee, M. (2010) Validating the prediction of lower urinary tract infection in primary care: sensitivity and specificity of urinary dipsticks and clinical scores in women. British Journal of General Practice, 60 (576), 495 -500. (doi:10.3399/bjgp10X514747). (PMID:20594439)

Record type: Article

Abstract

Background: Dipsticks are one of the most commonly used near-patient tests in primary care, but few clinical or dipstick algorithms have been rigorously developed.

Aim: To confirm whether previously documented clinical and dipstick variables and algorithms predict laboratory diagnosis of urinary tract infection (UTI).

Design of study: Validation study.

Setting: Primary care.

Method: A total of 434 adult females with suspected lower UTI had bacteriuria assessed using the European Urinalysis Guidelines.

Results: Sixty-six per cent of patients had confirmed UTI. The predictive values of nitrite, leucocyte esterase (+ or greater), and blood (haemolysed trace or greater) were confirmed (independent multivariate odds ratios = 5.6, 3.5, and 2.1 respectively). The previously developed dipstick rule — based on presence of nitrite, or both leucocytes and blood — was moderately sensitive (75%) but less specific (66%; positive predictive value [PPV] 81%, negative predictive value [NPV] 57%). Predictive values were improved by varying the cut-off point: NPV was 76% for all three dipstick results being negative; the PPV was 92% for having nitrite and either blood or leucocyte esterase. Urine offensive smell was not found to be predictive in this sample; for a clinical score using the remaining three predictive clinical features (urine cloudiness, dysuria, and nocturia), NPV was 67% for none of the features, and PPV was 82% for three features.

Conclusion: A clinical score is of limited value in increasing diagnostic precision. Dipstick results can modestly improve diagnostic precision but poorly rule out infection. Clinicians need strategies to take account of poor NPVs.

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More information

Published date: July 2010
Keywords: algorithms, clinical scoring, diagnosis, urinary tract infection, primary care, urinalysis
Organisations: Community Clinical Sciences

Identifiers

Local EPrints ID: 168275
URI: http://eprints.soton.ac.uk/id/eprint/168275
ISSN: 0960-1643
PURE UUID: 525e5903-38b7-4be1-b509-5c9db2a9b299
ORCID for M. Moore: ORCID iD orcid.org/0000-0002-5127-4509
ORCID for G. Leydon: ORCID iD orcid.org/0000-0001-5986-3300

Catalogue record

Date deposited: 26 Nov 2010 11:53
Last modified: 09 Jan 2022 03:19

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Contributors

Author: P. Little
Author: S. Turner
Author: K. Rumsby
Author: R. Jones
Author: G. Warner
Author: M. Moore ORCID iD
Author: J.A. Lowes
Author: H. Smith
Author: C. Hawke
Author: G. Leydon ORCID iD
Author: M. Mullee

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