PTT Advisor App, a clinical decision support for prolonged partial thromboplastin time (PTT)

The partial thromboplastin time (PTT) is a medical screening test that helps evaluate a person's ability to appropriately form blood clots, usually to detect any abnormalities in blood clotting or monitor the treatment effects with anticoagulant drugs, such as heparin. This test is sometimes called an activated partial thromboplastin time (APTT) test.

The PTT test measures the number of seconds it takes for a clot to form in a blood sample after a reagent is added. The typical reference range is between 30 and 50 seconds, depending on the laboratory.

The PTT test may be ordered when a person has unexplained bleeding or bruising, a blood clot or other conditions which can affect the normal blood clotting process.

Blood clotting is a part of reactions known as the coagulation cascade which is triggered in our bodies when bleeding occurs. The body uses coagulation to stop bleeding. First, cells called platelets create a plug to cover the damaged tissue, then the body's clotting factors interact to form a blood clot. 

A deficiency in clotting factors can prevent a clot from forming and lead to symptoms such as excessive bleeding, persistent nosebleeds, and easy bruising.

With a PTT test, a person's blood sample is compared to a normal reference interval for clotting time. When a sample takes longer than normal to clot, the PTT is considered "prolonged." 

Causes of a prolonged prothrombin time (PTT) can be inherited and acquired. They may include vitamin K deficiency, liver disease, heparin and/or warfarin administration, deficiency of prothrombin, fibrinogen, and other clotting factors, lupus anticoagulant (may be associated with thrombosis rather than bleeding), etc. 

Most of these conditions decrease blood's tendency to clot or create a dysfunction in one or more coagulation factors, while sometimes the body produces certain antibodies directed against one or more coagulation factors, such as the antiphospholipid antibody, affecting the function of these factors and interfering with the test.

The PTT test alone cannot diagnose a specific condition, but it can help healthcare providers learn if there are any abnormalities in blood clotting process. If so, providers can order more tests to see which blood clotting factor is deficient and the reason behind it.

The ability to recognize abnormal results and determine further, follow-up tests requires good clinical decision-making skills. There are many tools available for providers helping them make these decisions, including those for ordering and analyzing PTT tests.

In collaboration with experts in diagnostic coagulation, the Center for Disease Control and Prevention (CDC) developed the app called PTT Advisor that specifically focuses on PTT tests.

The app is an easy-to-use algorithm for diagnosing and evaluating patients with various bleeding abnormalities.  It enables clinicians to quickly select the appropriate follow-up tests to evaluate patients with a prolonged partial thromboplastin time (PTT) laboratory result and a normal prothrombin time (PT) laboratory result.

The app features a decision tree, which is designed as a series of Yes/No questions intended to guide providers quickly through the algorithm, thanks to the simple and easy-to-use interface.

The screen is simple and tap-oriented, with questions or statements provided in the top-half of the screen, and large buttons (Yes, No, and Continue) provided in the bottom-half of the screen. This makes the decision options easy to distinguish and tap, thus algorithm easy to follow. 

The initial two questions that start evaluation are: "Does the patient have prolonged PTT and normal PT?" and "Is the patient older than 6 months?"

Based on users' answers, the app tailors further questions to help determine possible causes for a prolonged partial thromboplastin time, for both pediatric and adult patients.

Additional information is available for most of the steps, and it's provided in the form of footnotes as a button in the upper-right portion of the screen.

At the end of the evaluation, the users can choose to view the "Evaluation Review" feature, which is also accessible at any time, allowing users to review all the selected steps in the algorithm and quickly modify any previously completed step in the algorithm.

This is a very handy way to start the evaluation over if a mistake was made, thus saving the precious clinician's time.

Also, this makes the app ideal for rapid decision making at the point of care, but it can be also used as a training or educational tool.

The algorithm provided in the app is very easy to use, however, the app provides Help section, which describes how the toolbar can be used.

PTT Advisor app doesn't require registration, login, or Internet connection, and it does not collect or store any users' or patients' data.

The app is available for iPhone, iPod touch or iPad for free, but currently, there's no version for Android.  

I would recommend PTT Advisor app to any clinician who need good, reliable decision-making support tool when selecting the appropriate follow-up tests to evaluate patients with a prolonged PTT and a normal PT laboratory result.

Benefit: The app would be useful to all providers diagnosing and evaluating patients with various bleeding abnormalities