Original Investigation
Pathogenesis and Treatment of Kidney Disease
Diagnostic Accuracy of Urine Dipsticks for Detection of Albuminuria in the General Community

https://doi.org/10.1053/j.ajkd.2010.12.026Get rights and content

Background

Urine dipsticks, an inexpensive accessible test for proteinuria, are widely advocated for mass screening; however, their diagnostic accuracy in the general community is largely unknown.

Study Design

Evaluation of diagnostic test accuracy in a cross-sectional cohort.

Setting & Participants

AusDiab, a representative survey of Australian adults 25 years and older (conducted in 1999/2000). Stratified cluster random sampling from 11,247 individuals participating in the biomedical examination; complete urinalysis data available for 10,944.

Index Test

Urine dipsticks (Bayer Multistix), with a positive result defined as ≥1+ or trace or higher protein.

Reference Test

Albumin-creatinine ratio (ACR), measured on a random spot urine sample. Reference test positivity was defined as ACR ≥30 mg/g or ACR ≥300 mg/g.

Results

Numbers of participants with ACR <30, 30-300, and ≥300 mg/g were 10,219 (93.4%), 634 (5.8%), and 91 (0.8%), respectively. The area under the receiver operating characteristic curve (AUC) for dipstick detection of ACR ≥30 mg/g was 0.8451 ± 0.0129 (SE) in men and 0.7775 ± 0.0131 in women (P < 0.001). The AUROC for dipstick detection of ACR ≥300 mg/g was 0.9904 ± 0.0030 in men and 0.9950 ± 0.0016 in women (P = 0.02). Dipstick result ≥1+ identified ACR ≥30 mg/g with 57.8% sensitivity (95% CI, 54.1%-61.4%) and 95.4% specificity (95% CI, 95.0%-95.8%) and identified ACR ≥300 mg/g with 98.9% sensitivity (99% CI, 92.1%-100%) and 92.6% specificity (99% CI, 92.0%-93.3%). A dipstick result of trace or higher identified ACR ≥30 mg/g with 69.4% sensitivity (95% CI, 65.9%-72.7%) and 86.8% specificity (95% CI, 86.1%-87.4%) and identified ACR ≥300 mg/g with 100% sensitivity (99% CI, 94.3%-100%) and 83.7% specificity (99% CI, 82.8%-84.6%). A negative dipstick result (less than trace) had a negative predictive value of 97.6% (95% CI, 97.2%-97.9%) for ACR ≥30 mg/g and a negative predictive value of 100% (99% CI, 99.9%-100%) for ACR ≥300 mg/g. The probability of an ACR ≥30 mg/g confirmed on laboratory investigation was 47.2% (95% CI, 43.9%-50.5%) based on a dipstick result ≥1+ and 27.1% (95% CI, 25.1%-29.2%) based on a trace or higher result.

Limitations

Isolated urine samples precluded assessment of test reproducibility. Urine specific gravity and pH were not recorded; therefore, the effect of urine concentration on test performance was not assessed.

Conclusions

A dipstick test result <1+ or less than trace has a high negative predictive value in the general community setting, with minimal risk of a missed diagnosis of macroalbuminuria. High false-positive rates emphasize the need for laboratory confirmation of positive results.

Section snippets

Participants

This analysis is based on cross-sectional baseline data from AusDiab (Australian Diabetes, Obesity and Lifestyle Study), a population-based study of Australian adults initially surveyed in 1999-2000. Details of the survey methods have been described.21 A stratified cluster sampling method was used to select a nationally representative sample of the noninstitutionalized Australian population 25 years or older. A total of 20,347 eligible individuals enrolled from 42 randomly selected urban and

Participant Characteristics

Of eligible participants with complete dipstick and laboratory urinalysis data (n = 10,944), 45.3% were men and mean age was 51.6 ± 14.4. Participant characteristics are listed in Table 1. Participants with albuminuria had an older age distribution and higher rates of diabetes, hypertension, previous cardiovascular events, and eGFR <60 mL/min/1.73 m2. Proportions of the cohort with measured ACR ≥30 mg/g or ACR ≥300 mg/g were 6.6% and 0.8%, respectively. Dipstick urinalysis returned a negative,

Discussion

Community-based cohort studies show that dipstick urinalysis predicts long-term risk of end-stage kidney disease and cardiovascular and all-cause mortality.4, 5, 6, 7, 8, 9 However, uncertainty exists about the utility of dipsticks as a screening tool in this setting. We found that in a population-based cohort, a dipstick reading ≥1+ identified individuals with ACR ≥30 mg/g with high specificity and strong negative predictive value. A dipstick reading of trace or higher maintained a similar

Acknowledgements

Support: Dr White is supported by a Capacity Building Grant from the Australian Government National Health and Medical Research Council. The AusDiab Kidney Study is a substudy of the AusDiab Study. In addition to support from the AusDiab co-coordinating team, led by Prof Paul Zimmet and A/Prof Jonathan Shaw at the Baker IDI Heart and Diabetes Institute, Melbourne, Australia, their sponsors, and the National Health and Medical Research Council of Australia (NHMRC grant 233200), the AusDiab

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    Originally published online March 16, 2011.

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