The laboratory doctor must communicate to the clinicians the data relating to the analytical imprecision of the various available tests. While the analytical phases are automated, easily controllable, and reproducible (the share of analytical errors is consistently around 10% of all errors), the phases involving the human operator are susceptible to many possibilities of error, and it is in this direction. Those efforts must be directed to improving the quality of endocrinological examinations.
Hyperfixation definition: In the case of hyperfixation and if the context is evocative, the diagnosis of stress fracture becomes very probable. The hyperfixation of a fracture of the iliac wing in the athlete does not involve any particularity. The curvature of the iliac wings can hide hyperfixation on the AP radiographs, and the realization of oblique views can be very useful.
Faced with the absence of any progressive risk, it may be quite legitimate to then wait for the radiographic controls. The scintigraphy is carried out in a hospital nuclear medicine department in several stages:
- A small amount of radioactive product is injected into a vein. This product, called tracer (or radiopharmaceutical product), differs depending on the organ studied.
- The tracer attaches itself to the organ’s structures and then emits signals (gamma rays). These are analyzed using a specific device (gamma-camera) placed in front of the area to be studied.
- The camera records the concentration of the radioactive product in the different parts of the organ concerned. The number of points is likely to vary depending on the regions examined.
Hyperfixation meaning is more important in the so-called hyperfixation zones or “hot spots”. These may correspond to an infectious focus, a tumor, a bone remodeling, a region secreting an abnormally high quantity of hormones, etc.
The points are less numerous in the zones of hypofixation or “cold points”, revealing the presence of a destroyed tissue or badly irrigated by the blood vessels.
The gamma camera is attached to a support that rotates around the patient’s body (tomograph) on some imaging devices. This system makes it possible to record cross-sectional images of the organ studied, taken from different angles: this is tomoscintigraphy. So now you know what is hyperfixation.
How to stop hyperfixation
Bone scintigraphy gives a two-dimensional representation of the region studied. They will make it possible to highlight anomalies of the bone tissue on the whole of the skeleton. The advantage of this examination is its very high sensitivity.
If there are no abnormalities or pathologies, the radiotracer appears homogeneously and symmetrically on the images of the bone. Any attack on the bone increases the activity of the osteoblastic cells and reveals hyperfixation of the radioactive phosphonate.
The process of examination:
The examination can be supplemented with a tomoscintigraphy (to avoid the superposition of bone structures), making it possible to locate any anomaly more precisely and at an earlier stage (in particular cancerous metastases, which would not yet appear on a normal X-ray). It is a so-called hybrid gamma-camera coupled with an X-ray scanner, which offers a cross-sectional representation of the bone structures.
After the examination, the patient can go home without an accompanying person. There are no side effects. The patient emits low doses of radioactivity for a short period of time, requiring no particular avoidance precautions for those around him or contacts, including young children and pregnant women.
Since hormone tests often do not have both the ideal characteristics of accuracy and precision, accurate tests should be used for diagnosis and precise tests for monitoring. (an example could be represented by the dosage of parathyroid hormone in the diagnosis of primary hyperparathyroidism and by the determination of calcium in the patient’s follow-up after parathyroidectomy).
Importance of hyperfixation
Increasing importance is given to the biological causes of variation in results. Regardless of the analytical variability, the concentration of each analyze does not remain constant over time in the state of health and disease but oscillates around a homeostatic point specific to the subject or general. Not all the causes of this variability are known, and in some cases, this variability can be very significant.
Among the causes of intra-individual variability can be mentioned:
- age, which can affect the concentration of a constituent in the blood in the first days of life, during adolescence, and in old age;
- The diet influences many tests (the most classic are the glucose load curve and the urinary excretion of hydroxyproline and calcium). There are common foods that have particular and relevant effects. Caffeine, for example, increases the concentration of glucose and alters the tolerance to the glucose load, reduces the circadian rhythm of cortisol, and increases the concentration of sodium, potassium, calcium, and magnesium in the urine;
- the specific secretory characteristics of the different hormones, such as the circadian rhythm, which determines different concentrations throughout the day, particularly relevant for ACTH and cortisol, and secretory peaks for GH;
- Posture: passing from the supine to the upright position leads to a reduction in blood volume by 10%, with a consequent increase in the concentration of proteins, enzymes, and protein hormones since only the protein-free fluid passes into the tissues.
