help for ais_tmpm
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Title

    ais_tmpm -- Trauma Mortality Prediction Model (AIS version)


Version

    Version 3.0.

    ICDPIC Version 3.0 requires STATA 8.0 or higher.  ICDPIC Version 3.0 has
    been tested in STATA 10 and STATA 11, but the authors believe it should
    also work without incident in STATA 8 and STATA 9.  If you have any
    problems using ICDPIC Version 3.0 in STATA 8 or STATA 9, please inform
    the authors.

    ICDPIC Version 3.0 may be installed from within STATA using the ssc
    command.  If you installed a previous version of ICDPIC from the SSC
    archives website using the ssc command, we suggest that you first delete
    it by typing ssc uninstall icdpic followed by ssc install icdpic.
    Alternatively, you may use ssc install icdpic, replace.  See help for 
    ssc.

    If you installed any previous ICDPIC files obtained directly from the
    authors, please delete them ALL (.ado, .hlp and .dta files) to avoid any
    conflicts with ICDPIC 3.0 files.

    Please enter complete variable names in the ICDPIC Version 3.0 dialog
    boxes.  Do not use abbreviations.

    New to Version 3.0 is the addition of a dialog box (.dlg) file associated
    with each individual ICDPIC Version 3.0 program (.ado) file.  To access
    the ICDPIC dialog box, and all the ICDPIC programs, type: db icdpic.
    Typing icdpic, as in earlier versions, will still work, but ONLY with
    icdpic.  For example, to access the AIS TMPM program directly, type: db
    ais_tmpm.  Typing ais_tmpm, as in previous versions, will produce an
    error.

    Fixed in ICDPIC Version 3.0 is the ability to use path\file names
    containing spaces.

    Fixed in ICDPIC Version 3.0 is the ability to run in STATA 11.0.

    Fixed in ICDPIC Version 3.0 is a bug that caused the triss program to
    crash if the rts variable was named anything other than "rts".

    New in ICDPIC Version 3.0 (trauma program only) is the ability to choose
    whether an AIS value of 6 automatically forces an ISS of 75 or to
    automatically have all AIS values of 6 changed to an AIS value of 5 and
    then have the ISS calculated normally.

    All dialog boxes in ICDPIC Version 3.0 have memory.  Each time a dialog
    box is opened within the same STATA session, it will remember the values
    last entered.

    All dialog boxes in ICDPIC Version 3.0 have the following buttons:

      OK executes the program and removes the dialog box from the screen.

      SUBMIT executes the program and leaves the dialog box on the screen.
             Note that if an error message is generated the dialog box may be
             minimized.

      CANCEL removes the dialog box from the screen and does nothing.
             Clicking on the close icon of the dialog box does the same
             thing.

      HELP leaves the dialog box on the screen and presents the program help
           file.  The HELP button has a question mark on it.

      COPY leaves the dialog box on the screen and copies the program command
           to the clipboard.

      RESET resets the values of the controls in the dialog box to their
            initial state, just as if the dialog box were invoked for the
            first time.  Each time a user invokes a dialog box, its controls
            will be filled in with the values the user last entered.  RESET
            restores the control values to their defaults.  The RESET button
            has an R on it.


Syntax

        db ais_tmpm

    The AIS TMPM (AIS Trauma Mortality Prediction Model) dialog box will
    open.  Follow the instructions.

                                      OR

        db icdpic

    The ICDPIC dialog box will open.  Choose AIS TMPM and click OK or Submit.
    The AIS TMPM (AIS Trauma Mortality Prediction Model) dialog box will
    open.  Follow the instructions.


Description

    ais_tmpm estimates patient probability of death,


                               Pd = normal(TMPM)


    where


 TMPM = (C0 + (C1 X I1) + (C2 X I2) + (C3 X I3) + (C4 X I4) + (C5 X I5) + (C6 X
>  S) + (C7 X I1 X I2)


    Pd is the mortality predicted by TMPM and normal is the standard normal
    distribution function.  I1 through I5 are the MARC values ordered with
    the greatest MARC value (worst injury) first, second greatest MARC value
    second, up to the fifth worst injury.  S is a Boolean value set to 1 if
    the two worst injuries occur in the same body region and 0 otherwise.  I1
    X I2 represents the interaction of the worst and second worst injuries a
    patient has sustained.  C0 through C7 are coefficients.

    See also the Options and Remarks sections for IMPORTANT information on,
    and requirements for, ais_tmpm.


Options

None


Remarks

    The user's data must contain AIS codes.  AIS codes in the user's data
    must be of type string.  AIS codes should have a width of 6 (predot
    portion of code only) or 8 (complete code).  The AIS code prefix must be
    the same for all AIS codes and numbered sequentially starting with 1, for
    example, ais1...aisN.

    ais_tmpm adds the following variables to a new copy of the user's data
    stored on disk:


        marc_1-marc_n: MARC value for AIS codes 1..n
        inj1-inj5: injuries (AIS codes) associated with the top 5 MARC values
            (5 worst injuries)
        marc1-marc5: top 5 MARC values (5 worst injuries)
        high1-high2: AIS body region of the two worst injuries (top two MARC
            values) respectively
        same_reg: Boolean variable to indicate if top two injuries occurred
            in the same body region
        AIS_TMPM: Trauma Mortality Prediction Model value
        AIS_POD: probability of death


    Variables AIS_TMPM and AIS_POD are rounded to the nearest 0.000001.

    ais_tmpm requires the use of lookup table mais_s.dta.  This data table is
    supplied.  See help for icdpic, specifically the LOOKUP TABLES part of
    the Remarks section.


    NOTES ON METHODOLOGY AND VALIDATION

    The Trauma Mortality Prediction Model (AIS TMPM) has the same goal as the
    ISS.  Both provide a single number summary of a patient's injuries when
    those injuries are described in the AIS lexicon.  However ISS considers
    only at most three of a patient's injuries, and provides only a relative
    measure of injury severity (0 to 75).  TMPM, by contrast, considers as
    many as 5 of a patient's injuries and results in an actual prediction of
    that patient's mortality (0% to 100%) based upon the injuries sustained.

    Although ISS and TMPM have similar goals, the models upon which they are
    based are quite different: ISS is simply the sum of the worst AIS
    severities in each of the three most severely injured body regions.
    TMPM, by contrast, is based upon a probit model that includes the five
    worst injuries (regardless of where they occur in the body), as well as
    terms that describe interactions and whether the two worst injuries are
    in the same body region.  A further difference is the source of
    information that ISS and TMPM use to assign severity to individual
    injuries: ISS uses the AIS severity created by panels of experts over the
    years while TMPM uses empirically derived values for each AIS code.
    These "Model Adjusted Regression Coefficients" (MARC values) were derived
    from 702,229 patients injured between 2001 and 2005 and cared for at
    trauma centers that provided information to the National Trauma Data
    Bank.

    The details of the mathematics behind the derivation of MARC values and
    construction and validation of the TMPM have been published (Osler T,
    Glance L, et al, A trauma mortality prediction model based on the
    Anatomic Injury Scale, Ann Surg 2008;247:1041-1048).  In this study TMPM
    provided predictions that were substantially more accurate, both in terms
    of discrimination and calibration, than did ISS.

    Perhaps adding to the appeal of the TMPM is the fact that a version of
    this model that uses injuries described in the ICD-9 lexicon is also
    available. (Annals of Surgery, in press.) Because administrative data
    often describe patient injuries in either the AIS or ICD-9-CM lexicon,
    but not both, we anticipate the two TMPM programs (ICD-9-CM TMPM and AIS
    TMPM) will be useful to researchers who perhaps are confronted with data
    sets in which patients are described in the AIS lexicon in some and
    described in the ICD-9-CM lexicon in others.

    Note that, although TMPM uses only anatomic injuries in its predictions,
    there in nothing precluding the addition of other information (age, GCS,
    etc.) to outcome predictions.  A logistic model predicting outcome for
    any patient data set can easily be constructed with the anatomic injury
    component of the model encapsulated in the TMPM value.  Note, however,
    that if TMPM is to be incorporated into a larger logistic model it should
    enter such a model as its logit (log(Ps /(1-Ps))) transformation.


Examples

    None


Authors

    David E. Clark, M.D.

        Maine Medical Center, Portland, Maine, USA
        University of Vermont College of Medicine, Burlington, Vermont, USA
        Harvard Injury Control Research Center, Harvard School of Public
            Health, Boston, Massachusetts, USA

    Turner M. Osler, M.D.

        University of Vermont College of Medicine, Burlington, Vermont, USA

        Correspondence to Dr. Osler,
        Department of Surgery
        University of Vermont
        789 Orchard Shore Road
        Colchester, VT 05446
        Email:  tosler@uvm.edu

    David R. Hahn

        Maine Medical Center, Portland, Maine, USA


References

    Osler T, Glance L, Buzas JS, Mukamel D, Wagner J, Dick A.  A Trauma
        Mortality Prediction Model Based on the Anatomic Injury Scale.  Ann
        Surg 2008;247:1041-1048.


Also see

    help for icd9tmpm

    help for icdpic