Fibroblast Growth Factor 23; FGF 23 Test
About Fibroblast Growth Factor 23; FGF 23 Test
| Field | Value |
|---|---|
| Also Known As | FGF-23, Intact FGF23 (iFGF23), C-terminal FGF23 (cFGF23), Fibroblast Growth Factor-23 |
| Sample Type | Plasma (EDTA tube) |
| Fasting Required | Overnight fasting (up to 12 hours) is recommended before this test |
| Report Time | 3 days |
| Recommended For | Males and females of all ages, particularly those with suspected phosphate disorders, rickets, or chronic kidney disease |
| Price | Starting at ₹7,700 |
What is a Fibroblast Growth Factor 23; FGF 23 Test?
The Fibroblast Growth Factor 23; FGF 23 test measures the level of Fibroblast Growth Factor 23, a hormone produced mainly by bone cells that regulates how the body handles phosphate and vitamin D.
Doctors order this test when investigating unexplained bone pain, low phosphate levels, or suspected kidney and bone metabolism disorders. A small blood sample, collected as plasma in an EDTA tube, is used for this test. It is also known as the Fibroblast Growth Factor-23 test, or simply the FGF-23 test.
What Does a Fibroblast Growth Factor 23; FGF 23 Test Measure?
This test measures the concentration of FGF23 in the blood. There are two types of assays used in laboratories, and your doctor will specify which is appropriate for your situation.
| Assay Type | What it Measures |
|---|---|
| Intact FGF23 (iFGF23) | Only the biologically active, full-length FGF23 hormone |
| C-terminal FGF23 (cFGF23) | Both the active hormone and inactive fragments are produced during processing |
FGF23 is a phosphaturic hormone, meaning it promotes the excretion of phosphate through urine. It is secreted primarily by bone cells (osteocytes) and plays a key role in keeping phosphate and vitamin D levels balanced in the body.
Why is a Fibroblast Growth Factor 23; FGF 23 Test Done?
The Fibroblast Growth Factor 23; FGF 23 test is a specialised test ordered when there is a clinical reason to assess phosphate metabolism or bone health. Below are the common reasons a doctor may request it.
Common Symptoms That May Require This Test
Several symptoms may prompt a doctor to consider the Fibroblast Growth Factor 23; FGF 23 test. These include:
- Bone pain or tenderness that does not have an obvious cause
- Muscle weakness affecting daily activities
- Unexplained fractures or fragile bones
- Persistent fatigue and low energy
- Loss of height over time
- Difficulty walking or a change in gait
- Symptoms suggesting low phosphate levels, such as general weakness
Conditions This Test Can Help Detect
This test helps identify a range of conditions linked to phosphate imbalance and bone metabolism. These include:
- X-linked hypophosphataemia (XLH), autosomal dominant hypophosphataemic rickets (ADHR), and autosomal recessive hypophosphataemic rickets (ARHR)
- Tumour-induced osteomalacia, a rare condition where a tumour causes abnormal phosphate loss
- Familial tumoral calcinosis with hyperphosphataemia, where abnormal calcium deposits form in soft tissues
- Chronic kidney disease (CKD), where FGF23 levels begin to rise in early stages
- Vitamin D deficiency, which is associated with low FGF23 levels
Fibroblast Growth Factor 23; FGF 23 Test for Chronic Disease Monitoring
FGF23 levels rise progressively in chronic kidney disease, often before phosphate levels or parathyroid hormone show changes. Monitoring FGF23 in CKD patients helps assess how the disease is progressing and how the kidneys are adapting.
In patients with FGF23-producing tumours, a drop in FGF23 levels after surgery indicates that the tumour has been completely removed.
How to Prepare and What to Expect
Proper preparation helps ensure your sample gives accurate results. The following guidance will help you get ready for the Fibroblast Growth Factor 23; FGF 23 test procedure.
Do You Need to Fast?
Yes, overnight fasting of up to 12 hours is recommended before the test. Fasting is preferred for the most accurate results, though it may not always be strictly required. If you have other tests ordered at the same time, check whether those also require fasting and plan accordingly.
Practical Tips Before Your Test
The following steps will help you prepare well for the test:
- Drink plain water to stay hydrated; this makes veins easier to find during blood collection
- Bring a detailed clinical history, including your symptoms, previous test results, and family history, as this is required for the test
- Inform your doctor about all medications, supplements, and any recent intravenous iron therapy, as these can affect results
- Avoid heavy meals and alcohol for 24 hours before the test
- Wear clothing with loose sleeves for easy access to your arm during sample collection
- Ensure you do not have iron deficiency (low ferritin) at the time of testing; discuss with your doctor if you are unsure
Step-by-Step Procedure
Here is what to expect during the Fibroblast Growth Factor 23; FGF 23 test procedure:
- A trained phlebotomist will ask you to sit comfortably and roll up your sleeve.
- The skin over the inner elbow area is cleaned with an antiseptic wipe.
- A tourniquet (a soft band) is wrapped around your upper arm to make the vein more visible.
- A small needle is inserted into the vein, and approximately 2 ml of blood is drawn into a lavender-topped EDTA tube.
- The tourniquet is removed, and gentle pressure is applied to the puncture site to stop any bleeding.
- The sample is refrigerated and sent to the laboratory promptly for analysis using the EIA (enzyme immunoassay) method.
Factors That Can Affect Accuracy
Several factors can influence the result of this test. These include:
- Iron deficiency, which can stimulate FGF23 production and alter results
- Recent intravenous iron therapy, particularly with ferric carboxymaltose
- Active inflammation or infection at the time of testing
- Reduced kidney function, which affects how FGF23 fragments accumulate in the blood
- High or low dietary phosphate intake in the days before the test
- Delay in sample processing after collection
Understanding Your Fibroblast Growth Factor 23; FGF 23 Test Results
Your results will show FGF23 levels in your blood. The table below provides general reference ranges; however, these vary depending on the assay type used by the laboratory. Always review your results with your doctor.
The following are simplified test result values as per age group:
- Pediatric (<18 yrs): < or =52 pg/mL
- Adults (> or =18 yrs): < or = 59 pg/mL
Also, the following table provides a detailed reference range for the individual assay type.
| Assay Type | Reference Range | Unit |
|---|---|---|
| Intact FGF23 (iFGF23) | 11.7 to 48.6 (some labs use up to 59 as the upper limit) | pg/mL |
| C-terminal FGF23 (cFGF23) | 21.6 to 91.0 (some labs use up to 150 as the upper limit) | RU/mL |
Disclaimer: These ranges are general guidelines. Your doctor will interpret your results based on your age, health history, and other factors. Always consult a qualified healthcare professional for personalised medical advice.
Results During Special Conditions
Certain health conditions can influence FGF23 levels independently of phosphate disorders.
Iron deficiency can stimulate FGF23 production. This effect is particularly pronounced in people with reduced kidney function, where low iron stores are common. Chronic kidney disease causes FGF23 to rise progressively as kidney function declines; levels can be very high in patients on dialysis.
Intravenous iron therapy, particularly with certain formulations, is also associated with temporarily elevated FGF23 values.
Inflammation and erythropoietin (EPO) therapy can affect how FGF23 is produced and broken down in the body.
How to Maintain Healthy Levels
These general wellness tips support normal phosphate and bone metabolism:
- Keep dietary phosphate intake balanced; avoid very high consumption of processed foods, which are often high in phosphate additives
- Ensure adequate vitamin D through safe sunlight exposure and vitamin D-rich foods
- Follow your doctor's guidance for managing chronic kidney disease, as this directly influences FGF23 regulation
Lupin Diagnostics Fibroblast Growth Factor 23; FGF 23 Test Price and Home Collection
The Fibroblast Growth Factor 23; FGF 23 test cost at Lupin Diagnostics starts at ₹7,700. Home sample collection is available for this test, making the Fibroblast Growth Factor 23; FGF 23 test online booking process convenient.
| City | Approximate Price (₹) |
|---|---|
| BHOPAL | 7700 |
| CHENNAI | 7700 |
| HYDERABAD | 7700 |
| NAVI MUMBAI | 7700 |
| PUNE | 7700 |
Disclaimer: Prices are indicative and may vary by location. Please confirm the current price at the time of booking.
How to Book
The Fibroblast Growth Factor 23; FGF 23 test online booking at Lupin Diagnostics is straightforward:
- Select the test on the Lupin Diagnostics website.
- Choose your city and preferred time slot.
- Opt for home sample collection by a certified phlebotomist, or visit your nearest Lupin Diagnostics centre.
- Receive your report via email or WhatsApp within 3 days.
Home Collection
The Fibroblast Growth Factor 23; FGF 23 test home collection service is available across cities, bringing certified phlebotomists to your doorstep at a convenient time. All samples are processed in NABL-accredited laboratories to ensure reliable results. Once ready, your report is delivered digitally via email or WhatsApp.
Frequently Asked Questions
The Fibroblast Growth Factor 23; FGF 23 test is used to evaluate phosphate metabolism in the body. It helps doctors investigate unexplained low phosphate levels, diagnose genetic bone disorders such as X-linked hypophosphataemia and hypophosphataemic rickets, and monitor the progression of chronic kidney disease.
Overnight fasting of up to 12 hours is recommended before the test for the best accuracy. In some cases, fasting may not be strictly mandatory, but following the recommendation is advisable. Check with your doctor or the laboratory for specific guidance.
Intact FGF23 measures only the biologically active form of the hormone. C-terminal FGF23 measures both the active hormone and inactive fragments. Intact FGF23 is generally preferred for patients with reduced kidney function, as inactive fragments can build up in the blood and give misleadingly high C-terminal readings.
At Lupin Diagnostics, the report is available within 3 days. As this is a specialised test processed using the EIA method, the turnaround time is longer than routine blood tests.
Yes. Iron deficiency is a known regulator of FGF23 production and processing. If you have low iron stores (low ferritin), your FGF23 levels may be affected. Inform your doctor if you suspect an iron deficiency before undergoing this test.
Yes, clinical history is required when submitting the sample. Bring details of your symptoms, previous test results, and any relevant medical records at the time of collection to ensure your sample is processed and interpreted correctly.
Elevated FGF23 can result from chronic kidney disease, recent intravenous iron therapy with certain formulations, or active inflammation. Your doctor will assess these factors alongside your results to determine the cause and decide on the next steps.
Fibroblast Growth Factor 23; FGF 23 Test
