Lab Indicators Explained

19 key lab indicators for ADPKD pacientes — meaning, mechanism, diagnostic value, estadio-based patterns, and seguridad guidance.

⚠ Medical Safety Notice

These explanations are for health education only. A single lab value does not establish a CKD estadio or tratamiento plan. Always interpret results with your nefrólogo, considering trends, clínico context, and your individual situation. Do not self-adjust medicamentos based on these values.

🫘 Renal Function Indicators

Estimated Glomerular Filtration Rate (eGFR)

Unit: mL/min/1.73m² Normal: ≥90 normal; 60-89 mildly decreased; 45-59 mild-moderate; 30-44 moderate; 15-29 severe; <15 insuficiencia renal

Purpose: Core indicator for assessing riñón filtración function, CKD staging, and disease progresión rate.

Frequency: As recommended by your doctor, typically every 3-6 months.

🔬 Measurement Methods & Standardization

Specimen & Method: Serum or plasma. eGFR is a calculated value from filtración markers and demographic parameters, not a direct measurement.

2021 CKD-EPI eGFRcr: Uses age, sex, and standardized serum creatinina. Limitations: muscle mass, recent cooked meat intake, muscle injury, and acute función renal changes can affect accuracy.
2021 CKD-EPI eGFRcr-cys: Combined estimation using age, sex, creatinina, and cyestatina C. Limitations: cyestatina C is also affected by inflamación, thyroid function, and glucocorticoids.

Standardization: Equations require IDMS-traceable creatinina and IFCC-standardized cyestatina C. Always compare results from the same laboratory using the same equation.

Pre-test considerations:

Record the equation name reported on the lab report.
Do not use a single eGFR during acute illness, dehydration, or sudden orina output changes to determine long-term estadio.
Patients under 18 or 18-25 need age-appropriate equations selected by a physician.

🩺 Clinical Application & Boundaries

Screening: Used with orina albumin-to-creatinina ratio to identify función renal and injury riesgo.

Monitoring: Serial trends are more valuable than a single number.

Risk stratification: ADPKD riesgo classification requires age, imaging, and disease course — eGFR alone is insufficient.

Diagnostic limits: eGFR below 60 for at least 3 months is part of the CKD definition. Structural ADPKD can exist when eGFR is normal.

Emergency significance: Acute decline, oliguria/anuria, or severe síntomas require urgent in-person evaluation.

📊 Interpretation

Target: Maintaining eGFR stability or slowing decline rate is the core tratamiento goal.

Range	Meaning	Action
≥90	G1: Normal or high filtración	Regular monitoreo, watch BP and TKV
60-89	G2: Mildly decreased	Control BP and proteínauria, annual check
45-59	G3a: Mild-moderate decrease	Check every 3-6 months, assess progresión
30-44	G3b: Moderate decrease	Check every 3 months, prepare for RRT education
15-29	G4: Severe decrease	Check every 1-3 months, initiate RRT education
<15	G5: Kidney failure	Initiate terapia de reemplazo renal

Factors: Age (natural decline ~1 mL/min/year), BP control, proteínauria, nefrotóxico drugs, dehydration, contrast media.

💡 Tip: Trends matter more than absolute values. Annual decline rate >5 mL/min suggests rapid progresión — discuss RAAP stratification and tratamiento options with your doctor.

🔗 Related Indicators & Sources

See also: Serum Creatinine (core input for eGFRcr); Cyestatina C (complementary estimation); Microalbuminuria (riesgo combination); Blood Pressure (progresión riesgo).

Related medicamentos: Tolvaptan; ACEI/ARB.

Sources: KDIGO 2024 CKD Guideline; NIDDK eGFR Equations for Adults.

⚠ Limitations: Estimated value, not direct measurement. Affected by age, muscle mass, and diet. May be normal in early ADPKD.

Serum Creatinine (SCr)

Unit: μmol/L Normal: Male 53-106; Female 44-97 (varies by laboratory)

Purpose: Traditional función renal indicator, used to calculate eGFR.

Frequency: As recommended, typically with eGFR.

🔬 Measurement Methods & Standardization

Specimen: Serum or plasma. The assay method and laboratory affect result comparability.

Jaffe method: Creatinine reacts with picric acid for colorimetric measurement. Widely used. Limitations: non-creatinina chromogens can interfere, especially at low creatinina levels.
Enzymatic method: Uses enzymatic reactions to measure creatinina. Generally higher specificity. Limitations: different platforms and calibration can still cause differences.
IDMS-traceable calibration: Aligns routine results with international reference measurement systems — the foundation for eGFR equation use. Limitations: cannot eliminate physiological variability from muscle mass, diet, or acute illness.

Standardization: When comparing trends, prefer the same laboratory and method. Record the unit (μmol/L or mg/dL).

Pre-test considerations:

Recent strenuous ejercicio or large amounts of cooked meat can transiently alter results.
Fever, vómito, diarrhea, oliguria, urinario obstruction, and new medicamentos should be recorded.
Do not substitute a single result for physician assessment.

🩺 Clinical Application & Boundaries

Screening: Primary input for eGFR calculation.

Monitoring: Interpret with baseline, eGFR, and cyestatina C trends.

Risk stratification: A single creatinina value cannot compare riesgo between pacientes of different body size, age, or sex.

Diagnostic limits: Creatinine elevation can reflect decreased clearance, increased genration, altered secreción, volume changes, or assay interference.

Emergency significance: Short-term significant elevation, oliguria/anuria, difficulty breathing, repeated vómito, high fiebre with dolor en el flanco, or gross hematuria all require urgent in-person evaluation.

📊 Interpretation

Target: Stable or slowly rising creatinina suggests stable función renal. Acute elevation requires attention.

Range	Meaning	Action
Within normal range	Kidney function relatively stable	Regular monitoreo
Mild elevation (1-1.5× upper limit)	Needs attention, interpret with eGFR	Recheck and discuss with doctor
Moderate elevation (1.5-2× upper limit)	Significant función renal decline	See doctor promptly
Acute rise (>25% short-term)	Possible acute riñón injury	Seek atención médica inmediata — check for dehydration, drugs, obstruction

Factors: Muscle mass (higher in athletes), age (lower in elderly), sex, diet (large meat intake can transiently raise), dehydration, nefrotóxico drugs (NSAIDs, contrast).

💡 Tip: Always interpret creatinina with eGFR. Results from the same laboratory are more comparable. Do not attempt to "lower creatinina" yourself — acute rise needs medical evaluation.

🔗 Related Indicators & Sources

See also: eGFR (estimation relationship); Cyestatina C (complementary check); BUN (joint assessment); Electrolytes (complicación assessment).

Related medicamentos: ACEI/ARB; Tolvaptan.

Sources: KDIGO 2024 CKD Guideline; KDIGO AKI Guideline.

⚠ Limitations: Affected by muscle mass, age, and sex. Less accurate than eGFR when used alone.

Cyestatina C (CysC)

Unit: mg/L Normal: 0.5-1.0 mg/L (varies by laboratory)

Purpose: Alternative filtración marker less affected by muscle mass, used for combined eGFR estimation.

Frequency: When creatinina-based eGFR may be inaccurate or near a tratamiento decision threshold.

⚠ Limitations: Affected by inflamación, thyroid dysfunction, and glucocorticoids. Not a direct GFR measurement.

Blood Urea Nitrogen (BUN)

Unit: mmol/L Normal: 2.9-7.5 mmol/L (varies by laboratory)

Purpose: Assesses riñón excreción function alongside creatinina. Affected by ingesta de proteínas, dehydration, and GI bleeding.

Frequency: Typically with creatinina.

⚠ Limitations: Highly affected by non-renal factors (diet, hydration, bleeding). Less specific than creatinina for función renal.

🧪 Urine Indicators

Urine Protein-to-Creatinine Ratio (UPCR)

Unit: mg/g Normal: <150 mg/g

Purpose: Estimates 24-hour proteína excreción from a spot orina sample.

Frequency: Every 3-6 months or as recommended.

⚠ Limitations: Affected by ejercicio, fiebre, and posture. A single elevated value should be confirmed.

Microalbuminuria (UACR)

Unit: mg/g Normal: <30 mg/g; 30-300 microalbuminuria; >300 macroalbuminuria

Purpose: Early marker of riñón damage, detects albumin-specific proteínauria before UPCR becomes abnormal.

Frequency: Annually or as recommended.

⚠ Limitations: Can be transiently elevated by ejercicio, fiebre, UTI, or heart failure.

🩸 Blood Indicators

Hemoglobin (Hb)

Unit: g/L Normal: Male ≥130; Female ≥115 (CKD-specific thresholds)

Purpose: Screens for CKD-related anemia (renal anemia due to EPO deficiency).

Frequency: Annually in early CKD, more frequently in advanced estadios.

⚠ Limitations: Must be interpreted with iron estudios. Other causes of anemia must be excluded.

Iron Metabolism (Ferritin, TSAT)

Unit: Ferritin μg/L; TSAT % Target (CKD): Ferritin >100, TSAT >20% (varies by guía)

Purpose: Assesses iron stores and availability before and during ESA therapy.

Frequency: With hemoglobina monitoreo in CKD.

⚠ Limitations: Ferritin is an acute-phase reactant — elevated in inflamación without iron overload.

💓 Blood Pressure Indicator

Blood Pressure (BP)

Unit: mmHg Target: <130/80 mmHg (per KDIGO; individualized)

Purpose: Hypertension is common and early in ADPKD. BP control is critical for slowing progresión and reducing cardiovascular riesgo.

Frequency: Home monitoreo regularly; clinic at every visit.

⚠ Limitations: Single readings are insufficient. Use validated monitors and proper technique. White-coat and masked hipertensión are common.

⚡ Metabolic Indicators

Uric Acid (UA)

Unit: μmol/L Normal: Male ≤420; Female ≤360 (varies)

Purpose: Hyperuricemia is common in ADPKD and can be worsened by tolvaptán. Monitor for gout riesgo.

Frequency: With renal function panels, especially during tolvaptán therapy.

⚠ Limitations: Elevated uric acid does not always require tratamiento — decision is clínico.

Lipid Panel (LDL-C, TC, TG)

Unit: mmol/L Target: LDL-C per cardiovascular riesgo (typically <2.6 in CKD)

Purpose: Assesses cardiovascular riesgo. CKD pacientes have elevated cardiovascular riesgo.

Frequency: Annually or as recommended.

⚠ Limitations: Interpret with overall cardiovascular riesgo, not in isolation.

🦴 Bone Mineral Metabolism Indicators

Parathyroid Hormone (PTH)

Unit: pg/mL Target (CKD G3-G5): ~2-9× upper normal limit (per KDIGO)

Purpose: Diagnoses and monitors CKD-MBD (enfermedad renal crónica-mineral and bone disorder).

Frequency: Every 3-6 months in CKD G3b-G5.

⚠ Limitations: Must be interpreted with calcio, phosphate, and vitamin D levels.

Electrolytes (K+, Na+, Ca²+, PO₄³-)

Unit: mmol/L K+: 3.5-5.0; Na+: 135-145; Ca²+: 2.1-2.6; PO₄³-: 0.8-1.5 (varies)

Purpose: Monitors for hyperkalemia, hyponatremia, and CKD-MBD abnormalities. Critical for medicamento seguridad (ACEI/ARB, diuretics, tolvaptán).

Frequency: With renal function panels, more frequently with medicamento changes.

⚠ Limitations: Potassium can be falsely elevated (hemolysis) — confirm critical values.

🫀 Liver Function Indicators

Liver Function (ALT, AST, Bilirubin)

Unit: U/L (ALT/AST); μmol/L (Bilirubin) Varies by laboratory

Purpose: Essential for tolvaptán seguridad monitoreo (hepatotoxicity riesgo). Also relevant for poliquistosis hepática assessment.

Frequency: As per tolvaptán monitoreo protocol (typically monthly initially, then quarterly).

⚠ Limitations: Mild ALT elevation can occur with many medicamentos. Pattern and magnitude matter more than single values.

🩹 Coagulation Indicators

Coagulation (PT/INR, APTT)

Unit: seconds / INR INR target varies by indication (e.g., 2.0-3.0 for atrial fibrillation)

Purpose: Monitors anticoagulation status in CKD pacientes (increased bleeding riesgo with declining función renal). Relevant for diálisis preparation.

Frequency: Per anticoagulation protocol.

⚠ Limitations: INR can be affected by hígado function, diet (vitamin K), and drug interactions.

🔥 Inflammation Indicators

C-Reactive Protein (CRP)

Unit: mg/L Normal: <10 mg/L (conventional); <3 mg/L (high-sensitivity)

Purpose: Marker of infection and inflamación. Important for distinguishing infección de quiste from other causes of dolor en el flanco.

Frequency: When infection or inflamación is suspected.

⚠ Limitations: Non-specific — elevated in many conditions. Must be interpreted clínicoly.

📸 Imaging Indicators

Total Kidney Volume (TKV)

Unit: mL (bilateral sum) Normal: ~200-300 mL (varies by age, sex, height)

Purpose: Key indicator for assessing quiste burden and disease progresión rate. Core parameter for Mayo Imaging Classification and RAAP estratificación de riesgo.

Frequency: Typically annually for estratificación de riesgo.

⚠ Limitations: TKV alone does not equal riesgo classification. Mayo Imaging Classification requires age, height, imaging method, and volumen total renal. Absolute volume without context should not be used to imply formal riesgo category — consult your physician for proper classification.

References

KDIGO 2025 Clinical Practice Guideline on ADPKD — KDIGO. View guía
KDIGO 2024 CKD Guideline — KDIGO. View PDF
NIDDK eGFR Equations for Adults — NIDDK. View page
KDIGO AKI Guideline (2012) — KDIGO. View PDF

🐛 Found an error in this page? Tell us

Evidence level: A–B (per KDIGO standard)
Limitations: Individual circumstances vary — always consulte a su nefrólogo.

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