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HelpTest Code STRC Standard Renal Clearance, Plasma and Random Urine
Specimen Required
Contact MLI for approval prior to ordering this test.
Both plasma and urine are required.
Specimen Type: Plasma
Container/Tube: 6-mL Green top (sodium heparin)
Specimen Volume: 3-4 mL
Collection Instructions: Label specimen as plasma.
Specimen Type: Urine
Container/Tube: Sarstedt 5 mL Aliquot Tube (T914)
Specimen Volume: 5 mL
Collection Instructions:
1. Collect a random urine collection.
2. No preservative.
3. Label specimen as urine.
Useful For
Precise measurement of glomerular filtration rate and renal plasma flow
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| IOTC | Iothalamate Clearance | No | Yes |
| PAHCC | PAH Clearance | No | Yes |
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Standard Renal ClearanceSpecimen Type
Plasma Na HeparinUrine
Specimen Minimum Volume
2 mL plasma/5 mL urine
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Heparin | Refrigerated (preferred) | 7 days | |
| Frozen | 7 days | ||
| Urine | Refrigerated (preferred) | 7 days | |
| Frozen | 7 days |
Reject Due To
| All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. |
Clinical Information
The assessment of glomerular filtration rate (GFR) is an important parameter of renal function utilized by clinicians in the care of patients with varying renal diseases, and for clinical research when precise assessment of renal function is necessary. The GFR is the sum of all the filtration rates of the individual nephrons within the kidney and, as such, reflects the number of functioning nephrons.
GFR can fall due to a chronic renal disease that causes a permanent loss of nephrons, or due to an acute renal injury that is potentially reversible. In addition, a decline in renal blood flow, ie, secondary to volume depletion, can result in a fall in GFR that is functional and (potentially) quickly reversible. GFR increases when factors that decreased renal blood flow are corrected, or the kidney heals after an acute injury. GFR also increases transiently during pregnancy, as well as in response to other physiologic stimuli that include hyperglycemia or a dietary protein load.
Measurement of GFR can be performed by several methodologies including creatinine clearance, iothalamate clearance, and inulin clearance. Of these methods, the latter 2 are significantly more accurate and reproducible than the former.
Renal clearance of inulin, a fructose polymer, has traditionally been considered the gold standard for determination of GFR. Disadvantages to the use of inulin are its high cost, limited availability, and analytical expense. Previous studies have shown close correlation between iothalamate and inulin GFR determinations. The short renal clearance test, which utilizes a subcutaneous injection of nonradiolabeled iothalamate and a single (1 hour) urine specimen, is the preferred method for measurement of GFR in most situations since it is less time consuming and less costly.
The Standard Renal Clearance test, which utilizes continuous intravenous infusion of iothalamate (or inulin) and additional urine and plasma collections, is an alternative means of measuring GFR and may be preferable in patients with low urine flows (eg, patients with severe liver failure).
The Standard Renal Clearance test also measures renal plasma flow (RPF). Intravenously administered para-aminohippurate (PAH) is used to determine RPF because PAH is nearly completely removed from the renal circulation in a single pass, by a combination of glomerular filtration and tubular secretion.
Reference Values
GLOMERULAR FILTRATION RATE
20 years: 87-141 mL/min/SA
(Iothalmate) Decreases by 4.95 mL/min/decade
≤ 19 years: Not established
20 years: 87-141
21 years: 86-140
22 years: 86-140
23 years: 85-139
24 years: 85-139
25 years: 84-138
26 years: 84-138
27 years: 83-137
28 years: 83-137
29 years: 82-136
30 years: 81-136
31 years: 81-136
32 years: 81-135
33 years: 80-135
34 years: 80-134
35 years: 79-134
36 years: 79-133
37 years: 78-133
38 years: 78-132
39 years: 77-132
40 years: 77-131
41 years: 76-131
42 years: 76-130
43 years: 75-130
44 years: 75-129
45 years: 74-129
46 years: 74-128
47 years: 73-128
48 years: 73-127
49 years: 72-127
50 years: 72-126
51 years: 72-126
52 years: 71-125
53 years: 71-125
54 years: 70-124
55 years: 70-124
56 years: 69-123
57 years: 69-123
58 years: 68-122
59 years: 68-122
60 years: 67-121
61 years: 67-121
62 years: 66-120
63 years: 66-120
64 years: 65-119
65 years: 65-119
66 years: 65-119
67 years: 64-118
68 years: 64-118
69 years: 63-117
70-150 years: 62-116
PARA-AMINOHIPPURATE (PAH) CLEARANCE
PAH Clearance
0-19 years: not established
20-29 years: >448 mL/min/SA
30-39 years: >413 mL/min/SA
40-49 years: >378 mL/min/SA
50-59 years: >343 mL/min/SA
60-69 years: >308 mL/min/SA
70-79 years: >273 mL/min/SA
80-89 years: >238 mL/min/SA
90-99 years: >203 mL/min/SA
Note: Reference range decreases by 35mL/decade.
FILTRATION FRACTION
>or=16 years: 18-22%
Interpretation
Iothalamate Clearance:
Low glomerular filtration rate (GFR) values indicate abnormal renal function, which may be either reversible/transient or irreversible/permanent. GFR tends to decline with age.
Para-Aminohippurate (PAH) Clearance:
The renal clearance of PAH, calculated from measurements of PAH in serum and timed urine specimens, equals renal plasma flow (RPF). However, it is important to note that only 85% to 90% of PAH is cleared from the circulation in a single pass, so the PAH clearance may underestimate RPF by 10% to 15%.
Filtration Fraction (FF):
The FF is the fraction of plasma perfusing the kidneys that is filtered (FF=GFR/RPF). Under normal conditions, FF is approximately 20%. Values significantly different from this provide an index to changes in GFR relative to RPF. For example, in states of decreased renal perfusion due to congestive heart failure, both RPF and GFR are decreased, whereas the FF is >20%.
Cautions
A theoretical complication (one that has not been observed clinically to date) is transient suppression of thyroid function in premature and newborn infants. Therefore, a sensitive thyrotropin test is suggested approximately 23 weeks after a standard renal clearance test in that age group.
Because complete clearance of para aminohippurate (PAH) is dependent on tubular secretion, diseases or conditions that disproportionately affect renal tubular cells may decrease PAH clearance without necessarily causing a proportional decrease renal plasma flow. Therefore, PAH clearance may underestimate renal perfusion flow in patients with selected diseases that affect renal tubulointerstitium.
Day(s) Performed
Monday through Friday
Report Available
Same day/1 to 4 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82542 x 7
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| STRC | Standard Renal Clearance | 96403-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| IOTC | Iothalamate Clearance | 90995-2 |
| PAHC | PAH Clearance | 96404-9 |
| FILT | Filtration Fraction | 96405-6 |
| CMT13 | Comment | 77202-0 |