BACKGROUND/RATIONALE:
Among individuals with diabetes, lower extremity amputation (LEA) is often a catastrophic complication leading to loss of ambulatory status and permanent disability. In FY2003, an overwhelming majority of (80%) all amputations performed in the Veterans Health Administration (VHA) occurred in veterans identified as having diabetes (Patient Care Services 2004 Amputation Rates Report). However, it has been proposed that nearly half of all LEAs can be prevented (CDC, 2003; CDC 2001). Consequently, a nationwide reduction in amputation rates is the goal of several current governmental initiatives. To our knowledge, there are no population-based longitudinal studies in VHA that address issues of progression to limb-threatening ischemia, non-traumatic incident LEAs (ILEA) including primary and secondary LE revascularization, repeat amputations and serious medical conditions among amputees. Our study aims to fill this serious gap in the literature and to provide critical insight into opportunities for quality improvement.
OBJECTIVE(S):
In this study, we propose to determine risk-adjusted incident lower extremity amputation (ILEA) rates, to examine the annual trends during the period of FY1999 to 2004, to investigate factors associated risks ILEAs, post-ILEA medical outcomes (repeat amputation, stoke, dialysis, death) as well as health care utilization (inpatient, outpatient, diabetes care, and specialty care) among veteran clinical users with diabetes.
METHODS:
A retrospective cohort analysis of VHA and Medicare combined data of diabetic veteran clinical users in FY99-03 with a follow-up period until FY04. Patients with diabetes will be identified using validated methodology developed by our group. Analyses: Annual rates will be estimated using indirect standardization method that we previously implemented in our work. We will employ generalized linear modeling using a logit link to model the amputation rates over time. Logistic regression and Cox proportional hazard models will be used to study risk factors associated with occurrence of study outcomes and time to post-ILEA medical outcomes. To model post-amputation care, we will use an episode-of-care approach.
FINDINGS/RESULTS:
We have been able to identify various problems associated with determination of ILEA (initial lower extremity amputation) and determined different methodologies to better identify ILEA. Overall, 2,997 (8.2 per 1,000) veterans experienced an amputation in fiscal year 2000. Using 24 months prior data, the rates of ILEA under the three different algorithms were 6.4/1000, 6.2/1000, and 6.0/1000. Using the most stringent algorithm, ILEA rates were 6.6/1000 with 12 months of prior data, 6.2 with 18 months of prior data. Compared to any amputations in FY 2000, 12, 18 months and 24 months look-back period decreased the ILEA rates by 19%, 24% and 27%, respectively.
In another project using 363,538 veteran clinical users with diabetes who were either VHA or dual VHA-Medicare-fee-for-service enrollees and alive as of the end of fiscal year (FY) 2000, we found 2,978 (8.2 per 1,000, 5.7~10.9 by VISNs) veterans experienced ILEA in fiscal year 2000. Of these, 2171 had ILEA (6.0/1000; 3.8~7.4), and 807 had RLEA (2.2/1000; 1.4~3.5). The Spearman statistic for correlation between risk adjusted VISN ranks for ILEA and LEA was 0.93 (p<0.001), and between RLEA and LEA was 0.86 (p<0.001). ILEA and RLEA ranks were moderately related (coefficient=0.67, p <0.001).
In another study involving VHA users with diabetes who were Medicare enrolled between fiscal year (FY) 1998 and 2000 (10/1/1997-9/30/2000). We found that 331,806 patients incurred a total of 4,037 (12.2 per 1,000 [range 9.3-16.7 across networks]) any amputations in FY 2000: 2271 major amputations (6.8 per 100 [4.7-9.1]) and 1766 minor amputations (5.3 per 1000 [3.9-7.6]). All the network outliers based upon the total amputation O/E ratio were also outliers based on major amputation O/E ratio. However, two of the five non-outliers based on total amputations were outliers based on major amputations. Simultaneous evaluation of major and minor amputation O/E ratios demonstrated four patterns of dual outlier status among networks: two networks had lower than expected minor and major amputation rates; two had higher than expected minor and major amputation rates; one network was lower than expected by major but higher by minor amputation rate; while one was higher than expected by major but lower by minor amputation rate.
We conducted a retrospective study of 1999 Large Veterans Health Survey (LVHS) respondents that were VHA clinic users with diabetes in fiscal years(FY) 1998-2000. Of the 114,890 individuals included in the study, there were 450 (3.9 per1000) major and 431 minor (3.8 per 1000) LEAs in FY2000. Individuals with major and minor LEAs had lower mental health functioning (i.e., lower average MCS score) than those without LEAs (39.9, 42.2, 43.4). After controlling for other independent variables, a five-point increase in MCS score was associated with 5% decrease in risk of major LEAs (OR=0.95, CI=(0.94, 0.96)). MCS was not related to minor LEAs. We concluded that footcare coordination programs need to incorporate both physical and mental health assessment and care to reduce risk of major amputation rates.
IMPACT:
1. Our findings on differential regional outcomes by amputation level was cited by the Organization of Economic Collaboration and Development to support their decision to utilize major, rather than total, amputation rates.
2. Our report that mental-health functioning is inversely correlated with future risk of major amputations within the next year was publicized by the American Psychosomatic Medicine.
PUBLICATIONS:
Journal Articles
- Tseng CL, Sambamoorthi U, Helmer D, Tiwari A, Rosen AK, Rajan M, Pogach L. The association between mental health functioning and nontraumatic lower extremity amputations in veterans with diabetes. General Hospital Psychiatry. 2007; 29(6): 537-46.
- Sambamoorthi U, Tseng CL, Rajan M, Anjali T, Findley PA, Pogach L. Initial nontraumatic lower-extremity amputations among veterans with diabetes. Medical Care. 2006; 44(8): 779-87.
