TITLE: withdrawal protocol for study of heavy metals in hair with edx
AUTHORS: Salvatore  Del Prete, Daniela   Marasco, Antonella  Cicale

[DESCRIPTION]
Whenever possible, it is preferable to take the sample from the area corresponding to the back of the head (vertex), as close as possible to the scalp;
in fact, it is considered that this region of the head is associated with a minimum inter-individual variability in the speed of hair growth. When the sample is taken on a child or on people with obvious hair thinning, there may be concerns about leaving them a bald spot. In these cases, the collection of the sample can be done by taking smaller strands in different areas of the head, however concentrating in the area of ​​the posterior vertex of the head.

The hair matrix of choice for the analyses is represented by hair, however, when their removal is not possible (for example baldness, zero shaving), alternative collection sites can be used such as the chest, pubis, armpits or the face (beard hair). The collection of samples in private parts of the body requires a careful assessment of the privacy of the subject subject to the control, while ensuring that the correctness of the collection process is not compromised. It should also be remembered that the growth rate and dormancy (telogenic phase) of the hairs collected in these areas of the body are different from the growth rate and dormancy of the hair. Therefore, it is not possible to go back to a time window of substance use, but one can only confirm or exclude a previous use.
The amount of hair required for the analysis is a lock of the thickness of a pencil, which can be divided into two parts (aliquot A and B). It is important to collect a sufficient quantity of hair to carry out both the screening and confirmatory analyses (aliquot A), as well as to keep a part of the sample for a possible verification analysis (counter analysis, aliquot B). The lock of hair to be removed must be fixed with a wire tied as close as possible to the skin before making the cut. In the case of short hair this is not possible. In this case, the cut strand is fixed on a sheet of paper with a clip indicating with an arrow the part proximal to the skin.

[BEFORE_START]
It is necessary to accurately document:
1. respect for the privacy and security of the subject under control at the time of collection;
2. verification of the identity of the subject subject to control;
3. the location where the sampling took place;
4. the correct attribution of the sample to the subject subject to control;
5. that no falsification or tampering with the sample has taken place;
6. that no unauthorized access to the sample has taken place;
7. that the informed consent has been signed by the subject under control;
8. the use by the subject under control of particular medicines that may interfere with the analytical results;
9. the traceability of the sample through appropriate records of its movements, from the place of sampling to its 
10. reception in the Laboratory, including the identity records of the personnel authorized to handle it

[GUIDELINES]
The collection of the sample must be carried out by a person authorized to carry out the collection itself. This person explains and carries out the procedure for taking the sample from the subject under control, completes the sampling report, has the informed consent signed and completes the appropriate sections of the chain of custody form. It is essential to prepare Standard Operating Procedures (SOPs) relating to the collection and storage of the sample, to the training of personnel assigned to take and transport the sample to the laboratory that will carry out the analysis. These procedures must be strictly followed.



[STEPS]
1. Roll and string a pencil-thick strand of hair or several thinner strands from the back of the head.
2. Hair should be cut immediately above the skin, as close to the scalp as possible. It is necessary to note the length of the hair strand.
3. The lock of hair must be placed in the appropriate aluminium foil. The portion of the lock corresponding to the roots must protrude from the toothed part of the sheet. PLEASE NOTE. THE OPERATION MUST BE REPEATED for rate A and rate B.
4. Each aluminium foil must be folded
5. The aluminium foil must be inserted in the appropriate envelope-container. The container-bag must be sealed
6. The envelope must be accompanied by the collection report and the chain of custody form. Rates A and B must be brought to the laboratory or sent by tracked priority mail or by express courier.