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§1  What is TRT control?

Therapeutic Range Time Control (TRT control) is an application aimed to calculate the time in therapeutic range for patients treated with Warfarin and/or Coumarin anticoagulants, based on their INR (International Normalized Ratio) values [1].

The input data are the patient's INR values, assumed to be the result of analysis on certain dates, and based on them, the application calculates the time in therapeutic range with two criteria (two results are obtained): the method of Rosendaal, and the commonly called conventional or "classic", wich is the quotient of dividing the number of samples in range by the number of total samples [2].

§2  Highlights

The application let choose between two bands for the Therapeutic Range: one more general, determined by the limits 2 and 3 for the INR, and between 2.5 and 3.5, which sometimes is considered adequate for patients with cardiac prosthesis.

In addition to the time in therapeutic range (conventional and Rosendaal's), the application provides some other values that may be useful for the clinician in their task of managing such patients:

  • Time over the maximum value of the chosen therapeutic range.
  • Time under the minimum value of the chosen therapeutic range [3].
  • Arithmetic mean of the INR values in the period.
  • Standard deviation of the INR values in the period [4].
  • Maximum deviation of INR over the upper limit of the range in the period.
  • Maximum deviation of INR under the lower limit of the range in the period.
  • Total period analyzed (days) between the first and last samples.
  • Total samples (number) in the period.
  • Arithmetic mean (days) for the intervals between samples.
  • Standard deviation of the intervals between samples [5].

Besides the above numerical values, the application provides a synoptic view of the patient's evolution in a graph, who in addition to the evolution along the time, and position of INR values relative to the used therapeutic range, show other parameters that are considered references in these pathologies [6].

Under certain circumstances, the application may show a small alert icon next to the numeric values. Clicking on it, a message is shown, who may be relevant as a wake-up call or warning to the clinician, who -perhaps with some time pressure- must act in response to the patient's state, reflected in the considered history.

In addition to the data associated with each sample analyzed (date and INR value), the application allows you to add a small note or comment to each input.

TRTc offers options to print the results and email them. In the latter case, in addition to the concept ("Subject:") and address ("Send to:"), the user can include carbon copy ("CC:") to a second address. The results are automatically included in the message body [7].

In this release, the application uses the Spanish language if that is the default on your Browser, or English otherwise (default). But there are an option to select which of these languages will be used in the future.

TRTc lets select the format of the dates among any of the three most frequently used:

  • dd-mm-yyyy day - month - year
  • mm-dd-yyyy month - day - year
  • yyyy-mm-dd year- month - day

TRTc can control any number of different patients, identified by an alphanumeric code that must be unique (supposedly, ID or SS Number) and an identifier, intended for the patient's name. Likewise, has a search facility that allows you to quickly select any of those included in the database (see below).

§3  Important observations

TRTc is not a substitute for clinical competence, although it can be a valuable aid to decision of the competent clinician. Note that although the application has been designed keeping in mind the health professionals, it can also be used as record for patients who want to monitor their prothrombin time (clotting) without paper and pencil.

It is important to note that the application makes no other data exchange with the Zator's Web server, that downloading the page, and the fact that the database created by the user, is contained in the browser of your own device, which results in several circumstances that should be taken into account:

  • Since the database belongs to the browser, if you use two browsers on the same device. I.e, Microsoft Internet Explorer and Google Chrome, although the Zator's server send both the same page when accessing our website, the data entered in IExplorer belong to this browser and will not be visible from Chrome and vice versa.
  • If you use two physical devices. For example, a desktop computer and a tablet or smartphone, even though both use the same type of browser. For example, Chrome, the data entered in the desktop will not be visible from the phone or tablet and vice versa (they are in different devices).
  • Remember that browsers have options to erase the data stored locally (browsing history), so that their use can erase the content of the user's data. For example, in Internet Explorer, the option "Security -> Delete Browsing History", delete the content of your database if you select the box "Cookies and website data". Meanwhile if in Chrome you select the box "Cookies and other site data and complements", the option "Tools -> Clear Browsing Data", will delete all data entered so far. Similar observations can be made regarding other browsers (Safari, Opera, Firefox, etc).


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[1]  INR is a way of express the prothrombin time, normalized by the World Health Organization. You can find a precise explanation of the concept in: "Lo que conviene saber a todo anticoagulado sobre el I.N.R." by Dr. Aguilera Vaquero.

[2]  Although the so-called "standard method" is easy to use in the lack of other tools, in certain circumstances may present important deviations from a more rigorous method as the one of Rosendaal. While the latter has the disadvantage of be more complicated and tedious to do manually.

[3]  Clearly, the sum of the (Roosendal) time, in rank; over the maximum and below the minimum, is equal to the total (100%) of the studied period.

[4]  This value is indicative of the stability (regularity) of the patient regarding his prothrombin time.

[5]  These two values provide a good indication of the quality of monitoring the patient regarding their clotting (frequency and regularity).

[6]  Based on the guide "Warfarin Therapy Management in Adults" by the Advisory Commitee of the Bristich Columbia Medical Association & Ministry of Health Services.

[7]  Assuming that the user's system has an available printer (or a remote printing service, such as Google Cloud Print) and a default email client.