Use and Interpretation of Urinary Albumin and Estimated Glomerular Filtration Rate Findings in Primary Health Care
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Aims: Chronic kidney disease (CKD) affects approximately 10% of the adult population. CKD patients have increased risks of morbidity and mortality, mainly from cardiovascular end points; early diagnosis and treatment is therefore warranted. CKD may be diagnosed based on an estimated glomerular filtration rate (eGFR) that is calculated from creatinine data, and the prognosis may be predicted based on urinary albumin excretion. The aim of this work was to elucidate how urinary albumin and eGFR are used and interpreted in the primary health-care setting. Another focus was to assess how the clinical chemistry laboratories that usually offer these tests interpret the test results. Methods: In all four studies, data were collected with the aid of a questionnaire. For Articles I and II, 10,000 general practitioners in 11 countries received a case-historybased questionnaire depicting a male type 2 diabetes patient. For Article III, 386 physicians received a questionnaire asking about 1 of their patients (selected from 2 different hospital laboratory databases) who had been diagnosed with CKD stage 3, based on eGFR results. For Article IV, 100 laboratory specialists in Norway and the Netherlands received a questionnaire regarding 2 case histories from primary health care (hypertensive and diabetic patients with laboratory results signalling possible renal disease) and 1 from a hospital setting. Results: The studies described in Articles I and II included 2078 general practitioners from 9 European countries. Almost all of the general practitioners recommended annual microalbuminuria testing in diabetic patients, whilst a lower frequency of testing was suggested for patients with hypertension or possible CKD. A spot urine sample prevailed for first-time office-based testing, whilst timed collections were used to a larger extent for hospital-based repeat testing. Of the 2078 general practitioners, 62% requested a repeat test to confirm the diagnosis if the first test was positive. Median values for the critical difference in albumin values was 33%, and four different measurement units were used. The absolute increase in the percentage of general practitioners who would supplement the patient’s drug treatment if microalbuminuria developed was 23–50% (depending on the country) for angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs), 0–19% for statins, 2–13% for acetylsalicylic acid and 0–33% for hypoglycaemic agents (tablets and insulin). For Article III, the response rate was 60%, and 210 patients were included. The median creatinine values were 95 and 124 μmol/l for female and male patients; the corresponding eGFR values were 52 and 51 ml/min/1.73m2. Only 27% of patients were assessed to have CKD stage 3. Twothirds had a urine dip strip (59%) and/or a urinary albumin (42%) measurement, and 20% were diagnosed with albuminuria (including both micro- and macroalbuminuria). Median changes to signal improvement or deterioration in renal function or indicating need for referral were 14 (12%), 20 (18%), and 40 (36%) μmol/l, respectively, for creatinine, and 8 (17%), 8 (17%) and 13 (26%) ml/min/1.73 m2 for eGFR. Albuminuria did not influence the follow-up strategy. For Article IV, 52 (52%) laboratory specialists responded. Based on guideline recommendations, less than 30% would suggest an optimal test panel for evaluating renal function in the two primary-care patients. For creatinine and eGFR, the median changes considered to signal improvement or deterioration in renal function (creatinine, 14% and 14%, respectively; eGFR, 18% and 13%, respectively) were similar to what could be calculated using information on analytical and withinsubject variations from the literature. The albumin:creatinine ratio varied (median values: 50% for improvement and 67% for deterioration). Conclusions: Guidelines for diagnosing microalbuminuria are only partially followed by general practitioners, and should be made more practicable, addressing issues such as type of samples, measurement units and repeat tests. Intensified drug treatment, and especially increased use of ACEIs and ARBs, was recommended to diabetic patients when microalbuminuria was present. CKD stage 3 patients were insufficiently examined for albuminuria and seemingly referred to hospital care only after the eGFR declined more than recommended in guidelines. Renal parameters are interpreted differently by laboratory specialists, and this could result in different advice being offered to clinicians, which again may affect patient care.
Paper I: Kristin M. Aakre, Geir Thue, Sumathi Subramaniam-Haavik, Tone Bukve, Howard Morris, Mathias Müller, Marijana V. Lovrencic, Inger Plum, Kaja Kallion, Alar Aab, Marge Kutt, Phillipe Gillery, Nathalie Schneider, Andrea R. Horvath, Rita Onody, Wytze Oosterhuis, Carmen Ricos, Carmen Perich, Gunnar Nordin and Sverre Sandberg: Postanalytical external quality assessment of urine albumin in primary health care: an international survey. Clinical Chemistry 54(10): 1630–1636, August 2008. Full text not available in BORA due to publisher restrictions. The article is available at: http://dx.doi.org/10.1373/clinchem.2007.100917Paper II: Kristin M. Aakre, Geir Thue, Sumathi Subramaniam-Haavik, Tone Bukve, Howard Morris, Mathias Müller, Marijana V. Lovrencic, Inger Plum, Kaja Kallion, Alar Aab, Marge Kutt, Phillipe Gillery, Nathalie Schneider, Andrea R. Horvath, Rita Onody, Wytze Oosterhuis, Carmen Ricos, Carmen Perich, Gunnar Nordin and Sverre Sandberg: Diagnosing microalbuminuria and consequences for the drug treatment of patients with type 2 diabetes: a European survey in primary care. Diabetes Research and Clinical Practice 89(2):103–9, April 2010. Full text not available in BORA due to publisher restrictions. The article is available at: http://dx.doi.org/10.1016/j.diabres.2010.03.023Paper III: Kristin M. Aakre, Geir Thue, Einar Svarstad, Øyvind Skadberg and Sverre Sandberg: Laboratory investigation and follow-up of chronic kidney disease stage 3 in primary care. Clinica Chimica Acta 412(11–12): 1138–1142, May 2011. Full text not available in BORA due to publisher restrictions. The article is available at: http://dx.doi.org/10.1016/j.cca.2011.03.004Paper IV: Kristin Moberg Aakre, Wytze Oosterhuis and Sverre Sandberg: How do laboratory specialists advice clinicians concerning the use and interpretation of “renal” tests? Scandinavian Journal of Clinical and Laboratory Investigation 72(2): 143-151, April 2012. Full text not available in BORA due to publisher restrictions. The article is available at: http://dx.doi.org/10.3109/00365513.2011.646298