Life Table Analysis System

Version History

The latest version of LTAS.NET is 4.0. It has enhanced features and fixes several known issues and bugs.

LTAS.NET 4.0 Enhancements and Bug Fixes

• Changes affecting software usability

  • Replaced SQL Server Express 2005 used in all LTAS.NET 3.0 versions with the 2014 version of SQL Server Express for better Windows compatibility and security.

• Support for Windows 7 SP1/8/8.1/10 64-bit

  • LTAS.NET 4.0 may be installed on computers with Windows 7 SP1, 8, 8.1, or 10 64-bit operating system.
  • Changed extension of project files from .ltas3 to .ltas4 to better facilitate upgrading from LTAS 3.0.
  • When opening a project in LTAS.NET 4.0, user can open and convert projects created in the previous version (3.0 or 2.0) of LTAS.NET in the dropdown menu.
  • Users may operate LTAS.NET 3.0 and 4.0 side-by-side if they have Windows 7 SP1/8/8.1/10 64-bit, although we recommend uninstalling LTAS.NET 3.0 as soon as feasible, because Microsoft will not provide security updates for its software platform (SQL Server Express 2005) beyond April 12, 2016.
  • The 32-bit version of Windows 7/8/8.1/10 is not supported.

• Changes affecting software functionality (Please refer to Appendix C in the user’s manual for variable ID description)

  • Corrected data requirement logic to reject History file records with partial Start or End dates (EC20r) and Person file records with partial Risk Begin dates (PC140r).
  • Corrected data requirement logic to reject persons with no person time (ST40r) so persons with 1 day of person time are not rejected.
  • Updated data requirement PC100w to PC100x to reject persons with date last observed prior to the rate file begin date (action changed from warning to exclusion).
  • Corrected documentation of rule PR20r from “DLO > Risk begin” to “DLO >= Risk begin”.
  • Corrected implementation of rule OC24r to exclude diagnoses when identifying the “earliest” outcome date and updated documentation.
  • Corrected a problem that caused LTAS to terminate completely instead of rejecting a person with an invalid risk begin date (PC140r).
  • Corrected a problem that prevented the requirement of a person having 1 or more histories in the study period (EP40r) from being enforced.
  • Updated actions to support non-terminal analyses:
    •  M50r now rejects any outcome (terminal or non-terminal) that is after the person’s DLO and rejects both the outcome and the person if the terminal outcome date is before the person’s DLO (this latter requirement was not previously enforced resulting in a person with an obvious error in their data (death date prior to DLO) erroneously contributing person-years at risk in a terminal study).
    •  OC23r now rejects both the outcome and the person if the outcome date is not in the rate file (previously, in non-terminal studies, an outcome prior to the rate file begin date would have been rejected, but the person was not, erroneously allowing the person to contribute person-years at risk).
    •  The requirement that a person’s outcome date be greater than or equal to their risk begin date (M60r) is now enforced (both the person and the outcome are rejected when the outcome date is prior to the risk begin date).
  • Updated M20r to only reject history records that begin prior to the person’s date of birth (previously M20r would reject history records that began on or prior to the subject’s date of birth).
  • Corrected Post-Stratify Personal Cumulative Dose report for unlagged cumulative level variables for cases who continued to work after their diagnosis date in non-terminal analyses.
  • Corrected a problem with the p-values reported in the Standardized Mortality Ratio (SMR) analysis. If ‘Report p-values instead of CI’ under ‘Confidence Interval or p-value’ in ‘Report Options’ was selected, the p-values would be reported incorrectly when the approximation formula was used (i.e., observed deaths greater than 20) and SMR<1 (i.e., Observed (D) less than the Expected (E)). All p-values are now correctly reported in LTAS 4.0.
  • Disabled time since first or last employment (TSFE/TSLE) in the horizontal variable dropdown menu in SRR analysis. This function is disabled due to a potential issue (“sparse data bias”) not related to LTAS algorithm.

• Changes to improve reports and data export capabilities

  • Added a missing report file that prevented SMR list reports with p-values from being generated.
  • Added the rule ID to the import exceptions and stratify rejects reports.
  • Changed the category order for an accumulating variable to be sorted by the cutpoint rather than by the label in Analyze reports.
  • Added the lag for employment status in the Analyze report when using a lag for employment status (Active vs. Inactive).
  • Added an option to report Person Days instead of Person Years to the Distribution of Person Years report.
  • Included strata that do not have rates in the cohort export.
  • Added a warning to all SRR reports “Warning: Presence of large imbalances in person-year distribution across categories can lead to biased SRR”.

LTAS.NET 3.0 Versions

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.
• 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.

LTAS.NET

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.