No that is not possible. Standards are calculated separately for each progress tests (see information about standards) and the standard of the December test applies exclusively to that test. It cannot be used to calculate outcomes on any other test.
You should first check whether you have included all key changes and cancelled questions when you calculated your score. Cancelled items are excluded when the percentage score is calculated (so if two questions are cancelled, you should divide by 198 instead of 200). If you still find a difference between your score and the official outcome, you should ask to look at your original test form. It is very likely that you will find differences between the original form and the copy you kept.
The definitive test results are determined after all key changes and cancelled questions have been processed, because at that point all errors have been removed from the test and the score can be determined accurately.
So, with a test of 200 items you will have a certain initial score, which may change due to key changes and cancelled questions. The true, definitive score is the score calculated after all key changes and cancelled questions have been processed, because the initial score was based on errors in keys and faulty questions.
A key change can be advantageous to some students (their score changes from negative to positive) and disadvantageous to other students (a change from negative to positive). That is only logical, there was a technical error, such as a typing error in the correct answer when the test was prepared.
When a question is flawed (for example: both answer options are correct, or the wording was wrong) it is cancelled. That means that all plus and minus points scored on that question are cancelled as well. This is logical too. When a question is cancelled, 1 is detracted from the number of questions in the formula used to calculate the percentage score: for example: 200 becomes 199, and the percentage score is calculated by dividing the absolute score by 1.99 instead of by 2.
If you look at a series of PGT results, the development of knowledge shows clearly, both for groups and for individual students. It is true that PGTs can vary in difficulty, and this may lead to a bend in the line representing the (group or individual) Correct minus Incorrect scores as well as changes in test standards (since these are norm referenced). Nevertheless it is quite possible to measure progress over a longer period of time, because a series of tests shows a reliable tendency of knowledge development (see for instance Van der Vleuten CPM and Driessen EW. Toetsing in probleemgestuurd onderwijs, Hoger Onderwijs Praktijk, Wolters-Noordhoff, Groningen 2000, 9. 27-32).
Moreover, you can see how your score compares with the score of your reference group. This comparison indicates if your score remains constant, improves or deteriorates compared to the group average, irrespective of the difficulty of the test.