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Life Table Analysis System


Version History

The latest version of LTAS.NET is 3.1. Below you will find changes and enhancements of various LTAS.NET versions.

Version 3

Version 3.1 includes the following enhancements:

  • The NIOSH-119 and NIOSH-92 underlying cause of death (UCOD) and NIOSH-119 multiple cause of death (MCOD) rate files have been updated with actual data through 2009.
Version 3.1 includes the following enhancements:
  • Corrected intermittent problem that caused last imported person record to be missing from the study database.
  • Corrected a problem with global risk begin date not being taken into consideration when rejecting persons whose risk end preceded the global risk begin.
Version 3.0.5 includes the following enhancements:
  • Updated NIOSH 119 Multiple Cause of Death (MCOD) rate files with data through 2007.
  • Updated the SQL Server 2005 package included in the full install to Service Pack 4 to resolve installation issues on Windows XP.
  • Corrected problem that caused LTAS to crash from selecting a global code revision when a non-ICD rate file is being used.
  • Corrected problem that caused importing a rate file to fail due to blank lines appearing within the RateData element.
Version 3.0.4 includes the following changes:
  • Corrected a problem with Export Rates function that caused the column headings to be listed in the wrong order.
  • Corrected a problem that prevented LTAS from locating standard rate files when installed under an account other than the user’s account.
  • Updated user manual with higher quality images for statistical formulas and mathematical equations.
  • A new version of the 92-cause map was included, with remapping of ICDA-8 cause 519.3 to minor 62 (chronic obstructive pulmonary disease).
Version 3.0.3 includes the following enhancements:
  • Corrected additional problem with exposure calculations in the Post Stratify PCD report that resulted in additional exposure to be reported for exposure that should have been completely lagged out.
  • Corrected a problem with exposure calculations in the Post Stratify PCD report that resulted in negative TSFE and TSLE values when exposure was lagged using days as units.
Version 3.0.2 includes the following enhancements:
  • Corrected a problem with exposure calculations in the Post Stratify PCD report that can result in lower and sometimes negative values to be reported.
Version 3.0 and Version 3.0.1 represent a major upgrade to LTAS.NET version 2.0. The changes are listed below:
LTAS.NET 3.0 Enhancements:
  • Support for Windows Vista and Windows 7
    • LTAS 3.0 may be installed on Windows 7, Vista, or XP.
    • Changed extension of project files from .ltas to .ltas3 to better facilitate upgrading from LTAS 2.0.
    • When opening a project in LTAS.NET 3.0, user is prompted to open and convert projects created in the previous version of LTAS.NET.
    • LTAS.NET 3.0 supports Windows XP, Vista, and 7 operating systems. If you install LTAS.NET 3.0 on an XP system that already has a previous version of LTAS.NET, you will notice that LTAS.NET 3.0 is installed side-by-side with your previous version of LTAS. You may use either version on a PC running XP; however, we recommend transitioning to LTAS.NET version 3.0 as soon as possible.
  • New rate file structure
    • The cause map and the rate file have been merged into a single file, which simplifies the importing of rates.
    • Rate files are easier to manage: they can be deleted from the default folder if no longer needed (this reduces the “clutter” in the rate pull-down box).
    • Updated US underlying and multiple-cause rates and proportions (for both 92- and 119-cause files) through 2007.
  • Changes affecting software functionality
    • Support for reporting p-values in SRR and SMR reports.
    • Changed the ordering of fields in the Import Wizard drop-down menu used to map fields so that they are ordered more logically (e.g., ID, sex, race, vital status, DOB, person-year begin date, date last observed, and any user-specified variables in the order entered), instead of alphabetically.
    • Changed the ordering of fields in the Import Options report so that they are ordered by column position (instead of alphabetically).
  • Changes affecting software usability
    • Updated Report Viewer to use SQL Server Reports, resulting in better export capabilities.
    • Updated Database Engine to use SQL Server 2005, doubling the storage capacity from 2GB to 4GB.
    • User documentation is now section 508 compliant.
  • Changes to improve reports and data export capabilities
    • Inclusion of Supermajor (“All Causes” and “All Cancers”) and Major cause-of-death categories in cohort export file.
    • Added a new capability in Stratify, allowing user to report or export the Post-Stratify Personal Cumulative Dose for each subject, which will give lagged cumulative exposures.
    • Changed analysis reports so that exposure lag information is included with the page variables.

Version 2

Bug Fixes since Version 2.0.16
  • Changed the way exposure lag time is calculated so that zero lagged cumulative exposure beyond the lag time period is appropriately mapped to the lowest exposure category.
  • Changed the Import data validation rule to allow for cases where "Risk Begin = DLO".
  • Changed Stratify to handle case where Effective Risk Begin = DLO.
  • Corrected a problem with person-time prior to achieving minimum exposure not being discarded.
  • Updated Stratify Reject report, export and progress dialog to account for person-time that is discarded.
  • Increased timeout values on all database queries to prevent timeouts on large studies.
  • Corrected a problem that caused stratify to fail if too many stratifier variables were selected. While a limit still exists, it is larger (see documentation for details).
  • Resolved Stratify issue that caused the wizard to fail when selecting a global categorical and no exposure agent.
  • Added validation to the Import Wizard to prevent duplicate names from being used for exposure agents, temporal categoricals, fixed stratifiers or global categoricals.
  • Resolved issue with exporting observed deaths and diagnosis for MCOD studies that caused the export file to be empty.
  • Enhanced the import data validation to reject history records with invalid exposure agent values.
  • Fixed problem that caused misaligned columns in the rate viewer when resizing the window.
  • Corrected a problem where the recoding of the “All other races” race category is not preserved when you switch between rates.
LTAS.NET Version 2.0.16

LTAS.NET version 2.0.16 was released in October 2008. This version included the following changes:

  • A table that shows the relationship between rate file and outcome file options has been added to the 'Outcome Import File' section of the documentation.
  • Corrected upgrade installation to properly restore custom rate files and cause maps. Custom rate files that were imported before an upgrade to a new version of LTAS.NET did not work properly under the following conditions:
    • The custom rate file referenced a custom cause map
    • Two or more custom cause maps were imported prior to the upgrade.
    • The custom cause maps were imported in an order other than alphabetical order.
    • After upgrading, users should re-import any custom rate files they are using. Even though the problem is now fixed and won't occur as a result of upgrading to this release, re-importing will eliminate the effects of previous upgrades.
  • Corrected Personal Cumulative Dose report to show correct person time in diagnosis-based studies for persons having multiple history records. For diagnosis-based studies, the Personal Cumulative Dose report was incorrectly including time after the date of diagnosis. This problem was specific to the Person Cumulative Dose report and did not affect any other reports including analysis reports.
  • Updated NIOSH-119 rates and cause map
    The NIOSH-119 UCOD and Proportion rate files have been updated with rate data for years 2003-2005. The LTAS.NET state rates have also been updated with the additional years of data. Additionally, the NIOSH-119 cause map file has changed slightly to correct the mapping for COPD in ICD Revision 8 along with a couple other minor re-mappings affecting Minors 64, 73 and 119.
  • Added support for diagnosis-based (i.e., incidence) studies
    • Changed import validation logic to properly handle diagnosis-based studies.
      See the Outcome File Requirements section in the LTAS.NET User's Guide for details.
    • For studies using diagnosis based rates, modify Stratify to include diagnosis for non-deceased persons.
    • Added ability to export observed diagnosis for studies that use diagnosis-based rates.
    • Corrected end of risk accumulation logic for diagnosis-based studies
    • Time at risk should not accumulate past the date of diagnosis for diagnosis-based studies. In addition to correcting the logic, the import wizard was changed to clarify the end of risk options for diagnosis-based studies.
  • Fixed problem causing incorrect results in SRR reports when all causes are selected
  • Selecting all causes for an SRR report caused incorrect results. In many cases, the same results were mistakenly reported for each cause.
  • Added support for revisions in non-ICD cause maps
    Studies that are based on non-ICD codes can specify either a global revision or specify the revision in the outcome file.
  • Corrected inconsistent calculation error when running Major/Minor Summary report.
    This removed an error message received when running a Major/Minor Summary report or any variant of an SMR List report that included Cause as the row variable.

In addition, the LTAS.NET FAQ and USER Manual documents have been updated.

Finally, the MCOD rates are now available for download. A separate mapping file is needed because these rates are still using the 1960-2002 data. They will be updated in the future to include the 2003-2005 data.

LTAS.NET Version 2.0.8

LTAS.NET version 2.0.8 was released in February 2008. This version corrected the following problems that had been identified in interim versions:

  • Fixed problem in person-year and event allocation for exposures occurring before follow-up time begins when a lag is also used.
  • Fixed problem with SMR analysis reporting incorrect expected and observed values in some situations.
  • Fixed rounding problem when stratifying Duration categories using Years for units.
  • Fixed errant warnings in Import Exception reports when a global risk begin date is used.
  • Modified 119 Mapping files to fix minor errors.

In addition, the LTAS.NET FAQ document has been updated.

LTAS.NET Version 2.0.1

LTAS.NET version 2.0.1 was released in September 2007. This version corrected two bugs: One bug occurred in Stratify for studies that have person-time and deaths extending beyond the last date for which rates are available (12/31/2004). If users included data beyond this date, the bug caused Stratify to crash the first time it encountered such a date. This bug was fixed by applying the rates from the previous five-year category to any person-time and events that occur after the end date of the rate files, based on the user-specified end of study date (up to five years beyond the last rate end date). The second bug affected only studies that imported time-since-last-exposure (TSLE) but not time-since-first-exposure for the exposure variable, and it caused TSLE to be inappropriately classified.


The new Windows-based version of LTAS, called LTAS.NET, was available for download in August 2007. The software is more interactive and provides greater flexibility for data input, export, and analysis. The U.S. underlying cause ratio and proportions are provided with LTAS.NET.

Objectives in creating LTAS.NET
  • Create a stable, user-friendly and reliable NIOSH life table analysis system for the Windows environment, as the DOS environment has become unreliable
  • Add features requested by users to increase utility of the program
  • Correct minor discrepancies noted in date handling and some statistical calculations within PC-LTAS
Major new features of LTAS.NET
  • User can stratify on and analyze
    • Two or more time-varying exposures simultaneously
    • User-defined fixed and time-dependent covariates
    • A global date for all persons in the cohort
    • Active employment status (with a user-defined lag for inactive status) to evaluate the healthy worker survivor effect
  • LTAS.NET has more flexible import, analysis and reporting options
  • User can export stratified event and person-time data for Poisson regression analysis

PC and Mainframe

The Life Table Analysis System (LTAS) was developed at the National Institute for Occupational Safety and Health (NIOSH) during the 1970s. Originally, LTAS was available only on IBM mainframe computer systems. During the 1990s LTAS was made available in a PC-DOS version called PC-LTAS. For a list of changes and enhancements since PC-LTAS, please see Major Differences between LTAS.NET and PC-LTAS . Please note that the PC-LTAS version is no longer available.