Challenges in Laboratory Lb Tests for CKD

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Brook George
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2 Challenges in Laboratory Lb Tests for CKD Hassan Argani Professor of Nephrology, Shahid Beheshti University of Medical Sciences

3 Introduction Challenge 1: Who should be screened for CKD Challenge 2: Which method is better for screening and follow up for CKD Challenge 3: The biases of each method

4 Introduction Challenge 1: Who should be screened for CKD Challenge 2: Which method is better for screening and follow up for CKD Challenge 3: The biases of each method

5 Revised chronic kidney disease classification based upon glomerular filtration rate and albuminuria GFR GFR stages (ml/min/1.73 m 2 ) G1 >90 Normal or high Terms G2 60 to 89 Mildly decreased G3a 45 to 59 Mildly to moderately decreased G3b 30 to 44 Moderately to severely decreasedd G4 15 to 29 Severely decreased G5 <15 Kidneyfailure (add D if treated by dialysis) Albuminuria stages AER (mg/day) Terms A1 <30 Normal to mildly increased (may be subdivided for risk prediction) A2 30 to 300 Moderately increased A3 >300 Severely increased (may be subdivided into nephrotic and non nephrotic for differential diagnosis, management, and risk prediction)

8 Introduction Challenge 1: Who should be screened for CKD Challenge 2: Which method is better for screening and follow up for CKD Challenge 3: The biases of each method

9 Who needs screening for CKD? The ACP recommendations, October 2013 The ASN in response to the ACP recommendations Asymptomatic adults without risk factors for CKD should not be screened for the disease (Grade: weak recommendation, low quality evidence Adults with or without diabetes who are currently taking an angiotensin converting enzyme (ACE) inhibitor or anangiotensinangiotensin IIreceptor blocker (ARB) should not be tested for proteinuria (Grade: weak recommendation, low quality evidence) CKD screening even in patients without ih risk ikfactors for CKD Disagreed. Present or absent Diabetes in adults taking an ACE inhibitor or an ARB, should be tested for proteinuria (Grade: weak recommendation, low quality evidence)

10 Flowchart for diagnosing CKD

11 How we should screen patients with CKD? All Patients Measurement of BP Serum Cr to estimate GFR Protein/Cr Ratio or Albumin/Cr Ratio in the first morning urine sample Examination of Urine Sediment or Test Tape for RBC and WBC Selected Patients Depending of Risk Factor Sonography Serum electrolytes l t Urinary Concentration Urinary ph

12 Diagnostic Evaluation in Chronic Kidney Disease-1 DISORDER CLINICAL URINE PROTEIN/CR CLUES SEDIMENT RATIO ADDITIONAL TESTS Diabetes mellitus Diabetes for > 15 years, Benign > 30 to > 3,500 mg of protein Fasting blood sugar, A1C retinopathy per g of creatinine Essential LVH, Benign > 30 to 3,000 mg No additional tests hypertension retinopathy of protein per gram of creatinine Glomerulonephritis History and Dysmorphic > 30 to > 3,500 C3 and C4 for all physical examination: infections; rash, arthritis; Old age RBCs or RBC casts mg of protein per g of creatinine patients Tests for infections: anti- ASO, ASK, HIV, HBsAg, HCV, RPR, blood cultures Tests if there is rash or arthritis: ANA, ANCA, cryoglobulin, anti-gbm Tests if patient is older than 40 years: SPEP, UPEP

13 Diagnostic Evaluation in Chronic Kidney Disease-2 URINE PROTEIN/CR DISORDER CLINICAL CLUES SEDIMENT RATIO ADDITIONAL TESTS Low flow Volume depletion, Hyaline casts, < 200 mg of protein FENa: < 1 percent; states hypotension, congestive heart failure, cirrhosis, atherosclerosis eosinophils per g of creatinine Urinary tract Urinary symptoms Benign, or None KUB radiography, obstruction RBCs intravenous pyelography, spiral CT scanning, renal ultrasonography Chronic urinary tract infection Urinary symptoms WBCs, RBCs < 2,000 mg of protein per g of creatinine Pelvic examination, urine culture, voiding cystourethrography, renal ultrasonography, CT scanning Neoplasm, Old ages, RBCs, RBC False-negative result SPEP, UPEP, calcium paraproteine mia constitutional symptoms, anemia casts, granular casts or > 30 to > 3,500 mg of protein per g of creatinine level, ESR Interstitial Medications, fever, WBCs, WBC 30 to 3,000 mg of ACE level; SS A, SS B nephritis rash, eosinophilia casts, protein per g of eosinophilia eosinophils creatinine

14 DISORDER Cystic kidney disease Renovascular disease Vasculitis Diagnostic Evaluation in Chronic Kidney Disease-3 URINE SEDIME CLINICAL CLUES NT Palpable kidneys with or without family history of cystic kidney disease, flank pain Late-onset or refractory hypertension, sudden onset of hypertension in young woman, smoking history, abdominal bruit Constitutionalsympt oms, peripheral neuropathy, rash, respiratory symptoms RBCs Benign PROTEIN/CR RATIO 30 to 3,000 mg of protein per g of creatinine < 200 mg of protein per g of creatinine ADDITIONAL TESTS Renal ultrasonography or CT scanning if there is a complex kidney cyst or mass Renal Doppler ultrasonography, radioisotope renal scanning, MRA, renal angiography RBCs; > 30 to > 3,500 mg C3, C4, ANA, ANCA; granular of protein per g of HBsAg, HCV, casts creatinine cryoglobulins, ESR, RF, SS A, SS B, HIV

15 Screening for Complications in CKD(Stages 3 and 4*) TEST Hemoglobin concentration Red blood cell indexes, reticulocyte count, iron studies, fecal occult blood test Serum electrolyte levels Calcium, phosphorus, and parathyroidhormone hormone levels Serum albumin and total protein levels COMPLICATIONS DETECTED Anemia For ruling out other causes of anemia before erythropoietin therapy is started Hyperkalemia, hyponatremia, acidosis i Hypocalcemia, hyperphosphatemia, secondary hyperparathyroidism Hypoalbuminemia, decreased levels of immunoglobulins in patients with nephritic levels of proteinuria or signs of malnutrition

16 Evaluation of Intrinsic Renal Failure Glomerular Vascular Interstitial Urinalysis RBC cast, OFB, fatty cast RBC cast None 24 h protein excretion (g/d/1.73 m2) > <2 Hypertension 50% 75% Rare

17 Introduction Challenge 1: Who should be screened for CKD Challenge 2: Which method is better for screening and follow up for CKD Challenge 3: The biases of each method

18 Minimalinitialdiagnostictests initial tests for patientswithckd Estimation of GFR Urinalysis Quantification of proteinuria Renal ultrasound Additional diagnostic tests, depending on the clinical situation Serologies for autoimmune diseases Serologies for chronic infections (hepatitis B and C, HIV, and others) Serum and urine protein electrophoresis and immunofixation Blood and urine cultures Imaging studies for malignancy Kidney biopsy??

19 Minimalinitialdiagnostictests initial tests for patientswithckd Estimation of GFR Urinalysis Quantification of proteinuria Renal ultrasound Additional diagnostic tests, depending on the clinical situation Serologies for autoimmune diseases Serologies for chronic infections (hepatitis B and C, HIV, and others) Serum and urine protein electrophoresis and immunofixation Blood and urine cultures Imaging studies for malignancy Kidney biopsy??

20 Minimalinitialdiagnostictests initial tests for patientswithckd Estimation of GFR Urinalysis Quantification of proteinuria Renal ultrasound Additional diagnostic tests, depending on the clinical situation Serologies for autoimmune diseases Serologies for chronic infections (hepatitis B and C, HIV, and others) Serum and urine protein electrophoresis and immunofixation Blood and urine cultures Imaging studies for malignancy Kidney biopsy??

21 Sensitivity and specificity of each equation to Diagnosisand and classify patients with CKD EPI CG: Cockcroft Gault equation; CGi: Cockcroft Gault equation (calculated with ideal weight); CKD EPI: the Chronic Kidney Disease Epidemiology Collaboration equation; CrCl: Creatinine clearance; MCQ: Mayo Clinic i Quadratic Equation; smdrd: simplified MDRD study equation.

22 Preferred Methods for Assessing Kidney Function METHOD MDRD study equation for estimating GFR SITUATIONS FOR USE Patients with diabetic kidney disease Patients with chronic kidney disease in middle-age (average age: 51 years) Black patients with hypertensive chronic kidney disease Patients with a kidney transplant Cockcroft-Gault equation for estimating creatinine clearance 24-hour urine collection for creatinine clearance Older patients (performs better than the MDRD study equation) Pregnant women Patients with extremes of age and weight Patients with malnutrition Patients with skeletal muscle diseases Patients with paraplegia or quadriplegia Patients with a vegetarian diet and rapidly changing kidney function

23 Formulas to Estimate Creatinine Clearance as an Estimate of GFR Cockroft Gault formula (ml/minute) (Cockroft, 1976): ([140 Age] [IBW])/(72 SCr) 0.85 if female. the CG formula overestimates the measured GFR at levels lower 60 ml/min/1.73 m2. The modified MDRD formula, 2000 GFR=175 Cr Age (for black) 0.742(for women) the MDRD underestimates the measured GFR at levels above 60 ml/min/1.73 m2. Males: IBW= 50kg+0.9 kg/cm over 150 cm Females: IBW= 45.5kg+o.95k k/c kg/cm over 150 cm

24 The formulas for estimating creatinine clearance for children Schwartz Formula 1976: GFR=0.55 hih( height(cm)/serum creatinine(mg/dl) i Counahan Barrett Formula 1976: GFR=40 height(cm)/serum creatinine(μmol/l) Modified Schwartz Formula in 2009: GFR(mL/min/1.73m2)=39.1[height(m)/Cr(mg/dL)]0.516 [1.8/cystatin C(mg/L)] 0.294[30/BUN(mg/dL)]0.169[1.099]male[height(m)/1.4]0.188 /dl)]0 099] [h ht( )/1 4]0 188 Most recently, a new formula, known as the CKD EPI (Chronic Kidney Disease Epidemiology Collaboration) equation, was reported to give improved performance over the widely used MDRD equation.

27 Introduction Challenge 1: Who should be screened for CKD Challenge 2: Which method is better for screening and follow up for CKD Challenge 3: The biases of each method

29 Tions Infection, Drug intoxication i ti Dehydration Obstruction Severe hypertension 1.5mg/dL

31 Cr production in male (mg/kg)= age Cr production in female (mg/kg)= age

33 Common causes of false estimates of elevated creatinine

34 Urea as Measure of Renal Function Urea is the main waste product of nitrogen containing chemicals in the body. It has a molecular weight of 60 Da. The concentration of urea is expressed only by the nitrogen content tof urea. Each molecule of urea contains 2 nitrogen atoms, the molecular weight of urea nitrogen is 28 Da. Serum urea is widely used as a measure of renal dysfunction, but its value as a measure of GFR is not very good for several reasons.

35 Causes of Prerenal Azotemia Low cardiac output Decreased plasma volume Decreased hemoglobin levels Endocrine dysfunction Renal dysfunction Vasodilation Acute myocardial infarction Chronic heart failure Valvular heart disease Diarrhea Vomiting Sweating Nasogastric suction Burns Diuretics Bleeding Uncontrolled diabetes mellitus (polyuria) Diabetes insipidus Addison disease Salt wasting nephropathy Sepsis syndrome Endotoxemia

36 Cystatin C Cystatin C is a 122 amino acid with a molecular weight of 13,000 Da. Is produced by all nucleated cells, and its production is constant. The rate of production is not affected by muscle mass, sex, or race. It is freely filtered and completely reabsorbed by the proximal tubule it is destroyed rather than reentering the circulation. It has no extrarenal elimination, so its plasma concentration is inversely related to GFR. Cystatin C is better than creatinine for estimation of GFR. However, cystatin C is not widely used clinically because measurements are difficult and expensive. The results of cystatin C equation were better than those achieved by the MDRD equation and the Schwartz formula for estimationof of GFR. Modified cystatin C equation: GFR[mL min(1.73m2)]=84.69 cystatin C (mg/l) (if a child<14years)

37 Level of Cystatin C is altered Increased Level Decreased Level Hyperthyroidism Peripheral arterial diseases Hypothyroidism Glucocorticostroids Metabolic syndrome Atherosclerosis Alzheimer Cigarette smoking Aorta Aneurysm CHF, MI, Stroke Malignancy HIV infection Increased CRP

41 Methods for GFR Estimation

Equations developed by the MDRD Study Group and CKD

Filtration Marker egfr Research Group Number of

Equati on MDRD Study creatinin i e 1999 Advantages

Ann 2002 Intern Med 1999; 130: 461-70; MDRD Study

above for standardized assay Study creatinin e 2006

Ann Intern Med 2006; 145: 247-54 CKD-EPI 12,150

42 Equations developed by the MDRD Study Group and CKD EPI, based on serum Cr. Filtration Marker egfr Research Group Number of subjects MDRD Study 1628 CKD Assays Nonstandardized Equati on MDRD Study creatinin i e 1999 Advantages Referen ces Recommended Levey et by NKF-KDOQI al. Ann 2002 Intern Med 1999; 130: ; MDRD Study Same as Re-expressed MDRD Appropriate p for Levey et above for standardized assay Study creatinin e 2006 use with standardized assays al. Ann Intern Med 2006; 145: CKD-EPI 12,150 Standardized CKD-EPI creatinin e 2009 Lesser bias ategfr >60. Recommended by KDIGO 2013 Levey et al. Ann Int Med 2009; 150:

43 Equations developed by the MDRD Study Group and CKD EPI, based on serum Cystatin CC Filtration Marker egfr Research Group Number of subjects Assays Equation Advantages References CKD-EPI CKD 3418 CKD-EPI cystatin C 2008 CKD-EPI creatininecystatin C 2008 Nonstandardized egfrcrcys more precise than egfrcr oregfr cys Stevens et al. Am J Kidney Dis 2008; 51: CKD-EPI Same as above Re-expressed for standardized assay CKD-EPI cystatin C 2011 CKD-EPI creatininecystatin C 2011 Appropriate for use with standardize d assays Inker et al. Am J Kidney Dis 2011; 58: d assays CKD-EPI Diverse 6471 Standardized CKD-EPI cystatin C 2012 CKD-EPI creatininecystatin C 2012 Lesser bias ategfr >60. Recommend ed by KDIGO 2013 Inker et al. N Engl J Med 2012; 367: 20-9

44 β 2 Microglobulin β 2 microglobulin, a polypeptide with molecular weight of 11.6 kda andlength of99aminoacids acids. Is a component of the MHA class I molecule. It is present in all nucleated cells, and is needed for production of CD8 cells. Its production is increased in multiple myeloma and lymphoma. β 2 microglobulin is freely filtered at the glomerulus, and then is reabsorbed and metabolized completely by the proximal tubule. Similar to cystatin C the plasma level increases in renal failure. The protein appears in the urine when reabsorption is incomplete because of proximal tubular damage, g, as in acute kidney injury.

45 β Trace Protein BTP is a low molecular weight glycoprotein with 168 amino acids. The molecular weight varies between and Da, depending on the degree of glycosylation. BTP belongs to the lipocalin protein family and functions as prostaglandin D synthase. Plasma BTP originates from the brain and is freely filtered at the glomerulus, l then is reabsorbed b completely ltl by the proximal ltubule and is catabolized there. The plasma level is increased in patients with renal disease because of reduced filtration in the presence of constant production. Estimated GFR by B Trace Protein is better than those obtained by the MDRD equation and serum cystatin C measurements. However, others showed that BTP was less sensitive than cystatin C. GFR=112.1 BTP urea (0.880 if female)

46 Tryptophan Glycoconjugate Is a substance normally produced in the body by glycoconjugation of tryptophan. It is filtered at the glomerulus freely and is not reabsorbed. A strong linear correlation exists between clearances of TG and inulin. TG increases progressively with declining renal function, but unlike creatinine, it is not affected by muscle mass. The current limitation: it can be measured only by the HPLC. It is not known whether dietary intake of tryptophan affects the serum concentration.

47 The soluble urokinase type plasminogen activator receptor The soluble urokinase type plasminogen activator receptor (supar) may be a marker of CKD. supar is a membrane protein that has been implicated in the pathogenesis of glomerular diseases including focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy.

48 Minimalinitialdiagnostictests initial tests for patientswithckd Estimation of GFR Urinalysis Quantification of proteinuria Renal ultrasound Additional diagnostic tests, depending on the clinical situation Serologies for autoimmune diseases Serologies for chronic infections (hepatitis B and C, HIV, and others) Serum and urine protein electrophoresis and immunofixation Blood and urine cultures Imaging studies for malignancy Kidney biopsy??

50 Complexity of Ui Urinary test t Collection Storage Analysis

52 APPEARANCE CAUSE Milky Acid urine: urate crystals Alkaline li urine: insoluble phosphates Infection: pus Spermatozoa Chyluria Smoky pink Hematuria (>0.54 ml blood/l urine) Foamy Proteinuria Blue or green Pseudomonas urinary tract infection Bilirubin Methylene blue Pink or red Aniline dyes in sweets Porphyrins (on standing) Blood, hemoglobin, myoglobin Drugs: phenindione, phenolphthalein Anthocyaninuria i (beetroot, t beeturia ) APPEARANCE CAUSE Orange Drugs: anthraquinones (laxatives), rifampicin i i Urobilinogenuria Yellow Mepacrine Conjugated bilirubin Phenacetin Riboflavin i Brown or black Melanin (on standing) Myoglobin (on standing) Alkaptonuria Green or black Phenol Lysol Brown Drugs: phenazopyridine, furazolidone, l dopa, niridazole Hemoglobin and myoglobin (on standing) Bilirubin

53 The main causes of false negative and positive testing from use of urine dipsticks Discounting contamination from menstrual or other bleeding, and exercise induced induced haematuria and proteinuria

54 Urinary protein Urinary protein excretion of < 150 mg/day is normal (~30 mg of this is albumin and about mg is Tamm Horsfall (muco)protein, derived from the proximal renal tubule). Protein excretion can rise transiently with fever, acute illness, UTIand orthostatically. In pregnancy, the upper limit of normal protein excretion is around 300mg/day mg/day. Persistent elevation of albumin excretion (microalbuminuria) and other proteins can indicate renal or systemic illness.

55 Microalbuminuria is an early sign of renal and cardiovascular Microalbuminuria is an early sign of renal and cardiovascular dysfunction with adverse prognostic significance.

56 AM PM AM

57 Albuminuria in the Detection of Renal Lesions Method of measurement (of choice): albumin/creatinine ratio (mg/g creatinine) Definition of albuminuria: >30 mg/g in spot urine sample Given measurement variability, 2 out of 3 positive measures are needed dover 3 6 months to consider it pathologic Valid samples: first morning, mid morning and mid afternoon urine samples Situationsthat that increase albuminuria:intenseintense physical exercise, fever, infection, heart failure, hyperglycemic decompensation False positives: hematuria, pyuria, highly concentrated urine Less accurate albumin/creatinine ratio in extreme values of creatinine: overestimated in reduced muscle mass and underestimated in muscular patients

58 The main causes of differently colored urine

59 Microscopic haematuria is present in around 4% of the adult population lti of whom at least 50% have glomerular disease

60 Conclusion

61 Summary of screening recommendations for CKD Screen four groups of patients with Diabetes Hypertension Cardiovascular disease Use two tests for screening Urine albumin to creatinine ratio in 2 to 3 spot urine samples (mg/g) Serum creatinine and egfr Age over 55 yr

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