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Assessment of proteinuria in patients with chronic kidney disease stage 3: albuminuria and non-albumin proteinuria

Assessment of proteinuria in patients with chronic kidney disease stage 3: albuminuria and non-albumin proteinuria
Assessment of proteinuria in patients with chronic kidney disease stage 3: albuminuria and non-albumin proteinuria
Background and Objective

Proteinuria assessment is key in investigating chronic kidney disease (CKD) but uncertainty exists regarding optimal methods. Albuminuria, reflecting glomerular damage, is usually measured, but non-albumin proteinuria (NAP), reflecting tubular damage, may be important. This study investigated the prevalence and associations of albuminuria and NAP, and the optimum number of urine specimens required.

Methods

1,741 patients with CKD stage 3, recruited from primary care, underwent medical history, clinical assessment, blood sampling, and submitted three early morning urine samples for albumin to creatinine ratio (uACR) and protein to creatinine ratios (uPCR). Albuminuria was defined as uACR ?3 mg/mmol in at least two of three samples. Isolated NAP was defined as uPCR ?17 mg/mmol in two of three samples and uACR <3 mg/mmol in all three. Prevalence and associations of albuminuria and NAP, degree of agreement between single uACR and average of three uACRs, and urine albumin to protein ratio (uAPR = uACR/uPCR) were identified.

Results

Albuminuria prevalence was 16% and NAP 6%. Using a <1 mg/mmol threshold for uACR reduced NAP prevalence to 3.6%. Independent associations of albuminuria were: males (OR 3.06 (95% CI, 2.23–4.19)), diabetes (OR 2.14 (1.53–3.00)), lower estimated glomerular filtration rate ((OR 2.06 (1.48–2.85) 30–44 vs 45–59), and high sensitivity CRP ((OR 1.70 (1.25–2.32)). NAP was independently associated with females (OR 6.79 (3.48–13.26)), age (OR 1.62 (1.02–2.56) 80 s vs 70–79) and high sensitivity CRP ((OR 1.74 (1.14–2.66)). Of those with uPCR?17 mg/mmol, 62% had uAPR<0.4. Sensitivity of single uACR was 95%, specificity 98%, PPV 90%. Bland Altman plot one vs average of three uACRs showed: mean difference 0.0064 mg/mmol (SD 4.69, limits of agreement ?9.19 to +9.20, absolute mean difference 0.837).

Conclusions

In CKD stage 3, albuminuria has associations distinct from those of isolated NAP (except for inflammatory markers). Single uACR categorised albuminuria but average of three performed better for quantification.
1932-6203
e98261
Fraser, Simon D.
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Roderick, Paul J.
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McIntyre, N.J.
f238f00e-bd97-4c2e-a779-9fde57365c5b
Harris, S.
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McIntyre, C.
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Fluck, R.
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Taal, M.W.
93cf9569-6e4e-4de5-9a6f-b30d7c41a28b
Fraser, Simon D.
135884b6-8737-4e8a-a98c-5d803ac7a2dc
Roderick, Paul J.
dbb3cd11-4c51-4844-982b-0eb30ad5085a
McIntyre, N.J.
f238f00e-bd97-4c2e-a779-9fde57365c5b
Harris, S.
19ea097b-df15-4f0f-be19-8ac42c190028
McIntyre, C.
d7d787f5-ae2e-442f-8d86-d9b9a806584b
Fluck, R.
986c578a-6f55-4f92-9ad3-e72f9f7dbe95
Taal, M.W.
93cf9569-6e4e-4de5-9a6f-b30d7c41a28b

Fraser, Simon D., Roderick, Paul J., McIntyre, N.J., Harris, S., McIntyre, C., Fluck, R. and Taal, M.W. (2014) Assessment of proteinuria in patients with chronic kidney disease stage 3: albuminuria and non-albumin proteinuria. PLoS ONE, 9 (5), e98261. (doi:10.1371/journal.pone.0098261). (PMID:24867154)

Record type: Article

Abstract

Background and Objective

Proteinuria assessment is key in investigating chronic kidney disease (CKD) but uncertainty exists regarding optimal methods. Albuminuria, reflecting glomerular damage, is usually measured, but non-albumin proteinuria (NAP), reflecting tubular damage, may be important. This study investigated the prevalence and associations of albuminuria and NAP, and the optimum number of urine specimens required.

Methods

1,741 patients with CKD stage 3, recruited from primary care, underwent medical history, clinical assessment, blood sampling, and submitted three early morning urine samples for albumin to creatinine ratio (uACR) and protein to creatinine ratios (uPCR). Albuminuria was defined as uACR ?3 mg/mmol in at least two of three samples. Isolated NAP was defined as uPCR ?17 mg/mmol in two of three samples and uACR <3 mg/mmol in all three. Prevalence and associations of albuminuria and NAP, degree of agreement between single uACR and average of three uACRs, and urine albumin to protein ratio (uAPR = uACR/uPCR) were identified.

Results

Albuminuria prevalence was 16% and NAP 6%. Using a <1 mg/mmol threshold for uACR reduced NAP prevalence to 3.6%. Independent associations of albuminuria were: males (OR 3.06 (95% CI, 2.23–4.19)), diabetes (OR 2.14 (1.53–3.00)), lower estimated glomerular filtration rate ((OR 2.06 (1.48–2.85) 30–44 vs 45–59), and high sensitivity CRP ((OR 1.70 (1.25–2.32)). NAP was independently associated with females (OR 6.79 (3.48–13.26)), age (OR 1.62 (1.02–2.56) 80 s vs 70–79) and high sensitivity CRP ((OR 1.74 (1.14–2.66)). Of those with uPCR?17 mg/mmol, 62% had uAPR<0.4. Sensitivity of single uACR was 95%, specificity 98%, PPV 90%. Bland Altman plot one vs average of three uACRs showed: mean difference 0.0064 mg/mmol (SD 4.69, limits of agreement ?9.19 to +9.20, absolute mean difference 0.837).

Conclusions

In CKD stage 3, albuminuria has associations distinct from those of isolated NAP (except for inflammatory markers). Single uACR categorised albuminuria but average of three performed better for quantification.

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Published date: 27 May 2014
Organisations: Primary Care & Population Sciences

Identifiers

Local EPrints ID: 365368
URI: https://eprints.soton.ac.uk/id/eprint/365368
ISSN: 1932-6203
PURE UUID: 30f9a620-8480-4acd-bab6-24287b5fc953
ORCID for Simon D. Fraser: ORCID iD orcid.org/0000-0002-4172-4406
ORCID for Paul J. Roderick: ORCID iD orcid.org/0000-0001-9475-6850

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Date deposited: 03 Jun 2014 10:45
Last modified: 20 Jul 2019 01:19

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Contributors

Author: Simon D. Fraser ORCID iD
Author: N.J. McIntyre
Author: S. Harris
Author: C. McIntyre
Author: R. Fluck
Author: M.W. Taal

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