Plasma

Plasma Separator Tube 4.5 mL

3 mL whole blood from light green top tube or 1 Microtainer®

Tissue or urine. Grossly hemolyzed or lipemic specimens.

24 hrs/day, 7 days a week, including holidays.

1 hour (upon receipt in laboratory)

Reference Interval (ng/mL)
AGE       MALE      FEMALE        AGE       MALE       FEMALE
0.25   12  -94.1   13.8-86.4      40     98.5-229     91.4-227
0.5    11.8-94.6   15.4-92        41     96.4-226     89.8-225
1      11.8-96.4   18.7-104       42     94.4-223     88.1-224
2      13.9-104    26.1-128       43     92.4-221     86.5-222
3      18.9-116    34.2-155       44     90.5-218     84.9-221
4      26.8-134    43.2-185       45     88.5-216     83.3-220
5      36.6-156      53-216       46     86.5-214     81.8-219
6      47.1-184    63.6-250       47     84.6-211     80.2-218
7      57.5-216      75-286       48     82.6-209     78.7-218
8      67.5-254    87.3-324       49     80.6-207     77.2-217
9      76.9-296    99.9-363       50     78.7-205     75.7-215
10     85.9-343     112-398       51     76.7-203     74.3-214
11     93.9-392     123-427       52     74.8-201     72.8-212
12      101-434     132-451       53     72.8-200     71.4-210
13      108-467     140-468       54     70.9-198       70-207
14      115-489     146-480       55     68.9-196     68.6-204
15      120-501     151-485       56       67-195     67.3-201
16      125-503     154-485       57     65.3-194     65.9-198
17      129-495     156-479       58     63.7-193     64.6-194
18      132-476     156-466       59     62.3-192     63.3-190
19      134-450     155-449       60     61.1-191       62-186
20      136-421     152-429       61       60-190     60.7-182
21      137-394     148-410       62     59.2-189     59.5-179
22      137-370     143-392       63     58.5-188     58.3-176
23      136-348     138-375       64     57.9-188     57.3-173
24      135-328     134-359       65     57.4-187     56.3-170
25      132-310     130-343       66     56.8-186     55.5-168
26      130-295     126-329       67     56.3-186     54.8-166
27      128-282     122-315       68     55.8-185     54.2-164
28      125-271     118-303       69     55.2-185     53.8-163
29      123-263     115-292       70     54.7-185     53.5-162
30      120-257     112-280       71     54.1-184     53.3-161
31      118-253     109-271       72     53.6-184     53.2-160
32      116-250     107-263       73       53-184     53.2-160
33      114-247     104-255       74     52.4-184     53.3-160
34      111-244     102-248       75     51.9-184     53.5-160
35      109-242     100-242       76     51.3-184     53.7-161
36      107-239    98.3-238       77     50.7-184       54-162
37      105-236    96.5-234       78     50.2-184     54.3-163
38      103-234    94.8-231       79     49.6-184     54.7-164
39      101-231    93.1-228       80                  55.1-166

The Z score is the approximate number of standard deviations a given result is above (positive score) or below (negative score) the age- and sex-adjusted population median. Z scores are calculated using the measured IGF-1 concentration and parameters provided by the assay manufacturer. Most results within the IGF-1 reference interval should have a Z score between -2.0 and +2.0, but in some cases IGF-1 results near the reference interval limits will not follow this pattern. Clinical correlation is recommended.

IGF-1 concentrations can be used to assess growth hormone (GH) deficiency or excess. Serum IGF-1 concentrations below the 2.5th percentile (Z-score < -2) are consistent with GH deficiency or severe GH resistance. Definitive diagnosis of GH deficiency or resistance may require additional diagnostic testing such as GH stimulation tests. The aim of GH replacement therapy in children and adults with GH deficiency is to achieve IGF-1 concentrations within the age- and sex-appropriate reference range, ideally the middle-to-upper third of that range.

Elevated IGF-1 concentrations help support diagnosis of acromegaly in conjunction with compatible clinical signs and symptoms. Additional diagnostic tests and imaging studies may aid in diagnosis.

Persons with anorexia or malnutrition often have low IGF-1 concentrations.

Reference ranges in pregnancy have not been formally established. IGF-1 concentrations increase approximately 2-fold during normal uterine pregnancy compared to pre-pregnancy baseline.

Note: Both patient age and sex are required for Z score calculation.

This assay may be significantly impacted by high-dose biotin (>5 mg dose) taken within previous 12 hours. High concentrations of biotin may lead to falsely decreased results. These concentrations may be found in patients taking over-the-counter supplements with biotin content much higher than nutritional requirements for biotin. Specimens should not be collected until at least 12 hours after the last dose.

References
1. Bidlingmaier M et,al: Reference intervals for insulin-like growth factor-1 (IGF-1) from birth to senescence: results from a multicenter study using a new automated chemiluminescence IGF-1 immunoassay conforming to recent international recommendations. J Clin Endocrinol Metab 2014 May;99(5):1712-1721.

2. Boquete HR et al: Evaluation of diagnostic accuracy of insulin-like growth factor (IGF)-1 and IGF-binding protein-3 in growth hormone- deficient children and adults using ROC plot analysis. J Endocrinol Metab 2003;88:4702-4708.

3. Brabant G: Insulin-like growth factor-I: marker for diagnosis of acromegaly and monitoring the efficacy of treatment. Eur J Endocrinol 2003;148:S15-S20.

4. Granada ML et al: Diagnostic efficiency of serum IGF-1, IGF-binding protein-3 (IGFBP-3), IGF/IGFBP-3 molar ratio and urinary GH measurements in the diagnosis of adult GH deficiency: importance of an appropriate reference population. Eur J Endocrinol 2000;142:243- 253.

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Electrochemiluminescence Immunoassay

Centrifuge at a speed and time necessary to get barrier separation of plasma/serum and cells within 1 hour of collection. Send specimen in original tube. Do Not transfer to another tube.
Each sample must be labeled with at least TWO full patient identifiers (First/Last Name & DOB are sufficient for non-UIHC affiliated clients) to avoid sample rejection/delays.

Refrigerate.
All sample storage requirements are intended for delivery to UIHC within 24 hours of collection for testing. If samples won't arrive in this time period, please call the UIHC Core Lab for alternative storage/shipping instructions (319-356-3527).

Place labeled specimen into zip-lock type biohazard bag; seal bag.
Place completed requisition into outside pocket of bag.
Transport in cooler with refrigerated coolant packs.

See also:
Insulin Like Growth Factor Binding Protein III (IGFBP-3), Serum
Insulin-Like Growth Factor II, Serum

See Additional Information:
Biotin Interference with Immunoassays