The POSAS consists of two parts: a Patient Scale and an Observer Scale. Both scales contain six items that are scored numerically and make up a ‘Total Score’ of the Patient and Observer Scale. The sum altogether will give the ‘Total Score’ of the POSAS. Besides the 10-step scale, category boxes are available to score nominal parameters (e.g. type of colour). Moreover, the patient and observer also score their ‘Overall Opinion’.
The six items and Total Score of the Patient and Observer Scale POSASv2.0
Each item of both scales has a 10-point score, with 10 indicating the worst imaginable scar or sensation. The lowest score is ‘1’, and corresponds to the situation of normal skin (normal pigmentation, no itching etc), and goes up to the worst imaginable. The Total Score of both scales can be simply calculated by summing up the scores of each of the six items. The Total Score will therefore range from 6 to 60. One may argue if the results of the separate items should be weighted to come to a more accurate Total Score. To date no convincing evidence is available that indicates that weighting improves the accuracy of the Total Score. Currently, the significance of weighting parameters is under investigation. Besides the six items the ‘Overall Opinion’ of the scar quality is scored separately of both patients and observers.
Categories (Observer Scale POSASv2.0)
Category boxes are provided to score the items not only quantitatively on a ten step scale but also qualitatively. In this way not only the severity but also the direction of the disorder (e.g., hypopigmentation or hyperpigmentation) is addressed. The categories are not included in calculating the Total Score of the POSAS. However, they are considered clinically relevant for complete documentation.
Overall Opinion (Patient and Observer Scale POSASv2.0)
Both the patient and the observer are asked to give their Overall Opinion on the appearance of the scar. Again, a 10-point scale is used in which 10 corresponds to the worst imaginable scar. The ‘Overall Opinion’ is not part of the Total Score of the Observer and Patient Scale of the POSAS.
Observer Scale POSASv2.0
In the POSASv2.0 observers rate vascularity, pigmentation, pliability, thickness, relief and surface area.
The directions for use of the different parameters of the Observer Scale POSASv2.0 are as follows (all parameters should be compared to normal skin at a comparable anatomical site whenever possible):
Vascularity: Presence of vessels in scar tissue assessed by the amount of redness, tested by the amount of blood return after blanching with a piece of Plexiglas
Pigmentation: Brownish coloration of the scar by pigment (melanin); apply Plexiglas to the skin with moderate pressure to eliminate the effect of vascularity
Thickness: Average distance between the subcuticular-dermal border and the epidermal surface of the scar
Relief: The extent to which surface irregularities are present (preferably compared with adjacent normal skin)
Pliability: Suppleness of the scar tested by wrinkling the scar between the thumb and index finger
Surface area: Surface area of the scar in relation to the original wound area
Furthermore the Overall Opinion is assessed as well as categories for each of the six items:
Vascularity*: pale | pink | red | purple | mix
Pigmentation: hypo | hyper | mix
Thickness*: thicker | thinner
Relief*: more | less | mix
Pliability*: supple | stiff | mix
Surface area*: expansion | contraction | mix
* If more options are applicable please select the most suitable option.
Patient Scale POSASv2.0
The Patient Scale contains six questions applying to pain, itching, colour, pliability, thickness and relief. Because it was too difficult for patients to make the distinction between pigmentation and vascularity, both characteristics were captured in one item: colour.
Each of the six items on both scales has a 10-point score, with 10 indicating the worst imaginable scar or sensation. The lowest score is ‘1’, and corresponds to the situation of normal skin (normal pigmentation, no itching etc), and goes up to the worst imaginable.
The Patient Scale POSASv2.0 contains the following questions:
1. Has the scar been painful the past few weeks?
2. Has the scar been itching the past few weeks?
3. Is the scar colour different from the colour of your normal skin at present?
4. Is the stiffness of the scar different from your normal skin at present?
5. Is the thickness of the scar different from your normal skin at present?
6. Is the scar more irregular than your normal skin at present?
These six items add up to the Total Score of the Patient Scale.
Besides those six questions, the patient is asked to provide an Overall Opinion concerning scar quality.
Number of observers
Normally scars are evaluated in a clinical situation. Draaijers et al showed in the original article that for evaluating burn scars, one observer suffices to come to a reliable Total Score of the Observer Scale. Two observers at least are mandatory if calculations are done on separate items. More observers will improve the reliability of the assessment in theory. For practical reasons the number of observers could be limited to three or four.
Conditions for assessment
Ideally, scars should be evaluated clinically under the same conditions such as room temperature and humidity. At the time of measurement the skin and scar tissue of the patient should be adapted to this situation. Especially pigmentation may change because of seasonal variation.
Scar evaluation by photographic assessment is not impossible but many of the parameters may be biased because of a suboptimal evaluation, e.g. pliability cannot be assessed adequately.