Tests

Your Organizational Guidance

ebpracticenet urges you to prioritize the following organizational guidance:

Chronisch nierlijden (multidisciplinaire aanpak)Published by: WORELLast published: 2017GPC pluridisciplinaire sur la néphropathie chronique (IRC)Published by: Groupe de travail Développement de recommandations de première ligneLast published: 2017

1st tests to order

renal chemistry

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Includes sodium, potassium, chloride, bicarbonate, BUN, creatinine, and glucose.

Serum creatinine alone is insufficient to determine chronic kidney disease (CKD) and may be falsely low in conditions of low muscle mass, as in older or malnourished people, or patients with liver failure.[72]

Normal creatinine in men is 0.8 to 1.4 mg/dL, and in women 0.6 to 1.1 mg/dL. However, there is significant variation due to calibration methods between laboratories.[2]

Electrolyte abnormalities may indicate an underlying cause of CKD, such as tubular disorders.[1]​ Adaptations in acid excretion by the kidneys initially prevent a fall in serum bicarbonate concentration, but as GFR declines, metabolic acidosis develops.[1]

Result

elevated serum creatinine; electrolyte abnormalities

estimation of GFR using serum creatinine

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A GFR estimating equation using serum creatinine is recommended for initial assessment.

Determines more accurately, by mathematical equations such as the chronic kidney disease (CKD) EPI equation, the GFR and the severity and stage of CKD.[73]

Interpretation of estimated GFR creatinine results should be individualized, including consideration of muscle mass. Reduced muscle mass may result in overestimation of GFR; increased muscle mass may lead to underestimation.[1]

In circumstances where creatinine-based eGFR is less accurate or uncertain (e.g., extremes of muscle mass, above-knee amputation, BMI >40 kg/m²), cystatin C should be measured, if available, and GFR estimated using a combination of creatinine and cystatin C, or cystatin alone.[1]

Laboratories should estimate GFR using an equation without a race variable.[54][55][56]​​ National Kidney Foundation: ​eGFR calculator Opens in new window

​​​ [ Glomerular Filtration Rate Estimation (eGFR) by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) Equation with Creatinine, without Race (2021) Opens in new window ] ​​​​​​​​​​

Result

<60 mL/minute/1.73 m²

estimation of GFR using cystatin C with or without serum creatinine

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In circumstances where creatinine-based eGFR is less accurate or uncertain (e.g., extremes of muscle mass, above-knee amputation, BMI >40 kg/m²), cystatin C should be measured, if available, and GFR estimated using a combination of creatinine and cystatin C, or cystatin alone.[1]

Laboratories should estimate GFR using an equation without a race variable.[54][55][56]​​ National Kidney Foundation: ​eGFR calculator Opens in new window

[ Glomerular Filtration Rate Estimation (eGFR) by CKD-EPI Equation with Cystatin C, without Race (2012) Opens in new window ] ​​​​​​ [ Glomerular Filtration Rate Estimation (eGFR) by CKD-EPI Equation with Creatinine and Cystatin C, without Race (2021) Opens in new window ] ​​​​​

Result

<60 mL/minute/1.73 m²

urinalysis

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Screening test to determine for pathologic markers of kidney damage excreted in the urine.

Result

hematuria and/or proteinuria

urinary albumin

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Urinary albumin assessment is preferred to total urine protein, with calculation of the albumin to creatinine ratio (ACR) or the albumin excretion rate (AER).[1][54]

Albuminuria is both a diagnostic and a prognostic variable in the evaluation of patients with chronic kidney disease (CKD).[2][57]

Moderately increased albuminuria is a risk factor for the development of progressive CKD and coronary artery disease associated with diabetes and hypertension. Indicated in patients with diabetes and CKD if there was no evidence of proteinuria on urine dipstick.[74]

Result

moderately increased (AER 30-300 mg/24 hours; ACR 30-300 mg/g

renal ultrasound

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Used to evaluate kidney size, mass lesions, urinary tract obstruction, and, with a duplex examination, renal arterial flow.[59][60]

Ultrasound is indicated in patients with a history of kidney stones or obstruction, renal artery stenosis, frequent urinary tract infections, or a family history of autosomal dominant polycystic kidney disease.[59]

Chronicity (duration of at least 3 months) may be established by imaging findings (e.g., reduced kidney size and cortical thickness).[1]

Result

small kidney size; presence of obstruction/hydronephrosis; kidney stones

Tests to consider

kidney biopsy

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Helps to determine pathologic diagnosis of chronic kidney disease in glomerular nephrotic and nephritic syndromes, or in people with diabetes with atypical presentations such as rapidly progressive kidney failure.

Also essential in determining whether pathologic lesions are due to infection (e.g., hepatitis B and C, syphilis, and streptococcal pharyngitis).

Chronicity (duration of at least 3 months) may be established by pathologic findings (e.g., fibrosis and atrophy).[1]

Provides insight into treatment options based on severity or chronicity of scarring of glomeruli and interstitium.

Result

variable depending on etiology

plain abdominal radiograph

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Nonspecific test that may aid in the detection of calcium-containing kidney stones.

Pure uric acid stones and most drug-related kidney stones are not apparent on plain radiography.[75][76]​​

Result

may reveal calcium-containing kidney stones

diabetes screen

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If not already known, consider screening for diabetes.

See Type 2 diabetes mellitus in adults.

Result

hyperglycemia

mineral bone disorder assessment

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Assessment for hyperparathyroidism includes measurement of calcium, phosphorus, and intact parathyroid hormone (PTH) levels.[62]

Frequency of monitoring depends on stage, with more frequent testing as chronic kidney disease stage increases.

Result

low serum calcium; elevated serum phosphorus; elevated serum intact PTH

anemia assessment

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Complete blood count (CBC) and iron studies are recommended to assess for anemia.

CBC should include hemoglobin concentration, red cell indices, white blood cell count and differential, and platelet count.[61]

Iron studies include serum ferritin and serum transferrin saturation (TSAT).

Measurement of vitamin B12 and folate may also be considered to assess for deficiencies.

Result

low hemoglobin; serum ferritin and TSAT levels will depend on presence of iron deficiency; serum vitamin B12 may be low; serum folate may be low

Emerging tests

genetic testing

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May be useful in establishing cause and, in some cases, informing management.[1][64][65]​ Actionable genes in kidney diseases have been suggested based on expert consensus.[1][20]

Result

positive for genetic variant in chronic kidney disease-related gene, e.g., APOL1, COL4A3, COL4A4, COL4A5, NPHS1, UMOD, HNF1B, PKD1, PKD2

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