DXA-Generated Z-Scores and T-Scores May Differ Substantially and Significantly in Young Adults

Central dual-energy X-ray absorptiometry (DXA) is the gold standard for non-invasive measurement of bone mineral density (BMD). Using this value and subject demographics, DXA software calculates T-scores and Z-scores. Professional society guidelines for the management of osteoporosis are based on T-scores and Z-scores, rather than on the actual BMD value. Although one expects T-scores and Z-scores to be very similar in young men and women for any given BMD measurement, little literature exists on this issue. Our clinical experience shows that some younger adult individuals (premenopausal women and men younger than 50 yr) have larger than expected difference between their DXA T-score and Z-score. This cross-sectional study evaluates the extent of this discordance between Z-scores and T-scores in a sample of 4275 men and women aged 20–49 yr. All subjects were scanned by central DXA using equipment manufactured by GE Lunar, GE, Madison, WI, or Hologic, Inc., Bedford, MA. Significant differences between Z-scores and T-scores were seen within individuals at the lumbar spine, total hip, femoral neck, and trochanter (p value < 0.001) for both DXA systems. Although these differences were less than half a standard deviation (SD) in most instances, the magnitude of difference was substantial at times, being 1 or more SD in up to 11% of cases (range: −1.95 to +1.54 SD). The smallest differences were seen at the total hip and the largest differences were seen at the femoral neck for both technologies. This is in part because there is no single standard Z-score definition, resulting in different methods of calculation across, and even within, DXA manufacturers. Standardization of Z-score definition and method of calculation is indicated. DXA Z-scores should be interpreted with caution in men and women aged 20–50 yr.     

Controversies in the management of cerebrovascular disease in older patients.

Several ongoing studies are evaluating the optimal management of patients with cerebrovascular disease. The Carotid Artery Stenosis with Asymptomatic Narrowing: Operation Versus Aspirin (CASANOVA) study has shown that carotid endarterectomy is not recommended for asymptomatic patients with less than 90% carotid stenosis. The North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgical Trial (ECST) have demonstrated that endarterectomy should be considered for patients who had recent carotid artery territory ischemic symptoms associated with angiographically defined stenosis of greater than 70%. These and other trials are expected to provide further data regarding management of cerebrovascular disease, including treatment of those patients with moderate (30 to 69%) carotid stenosis. Until that time, treatment decisions must be made on a case-to-case basis.     

Segmental intestinal muscular thinning: a possible cause of intestinal obstruction in the newborn

Intestinal obstruction proximal to a transition zone without an interposed physical barrier usually indicates Hirschsprung disease. The authors report one case of focal small bowel muscular thinning just distal to a transition zone that produced clinical and radiographic findings that simulated long-segment Hirschsprung disease in a 2-day-old infant.     

Quality of life in inflammatory bowel disease.

Quality of life with inflammatory bowel disease has not been well examined. Recently, a questionnaire to determine subjective health status for patients with inflammatory bowel disease has been developed and verified. To examine the quality of life in a group of "well" outpatients with inflammatory bowel disease, we developed a self-administered form of this questionnaire containing 36 questions identifiable to five dimensions: systemic symptoms, bowel symptoms, functional impairment, social impairment, and emotional function. We identified outpatients with inflammatory bowel disease through the local chapter of the Ileitis and Colitis Foundation and distributed 396 questionnaires, by mail, with 182 being returned completed (46% response rate). Forty-eight age- and sex-matched controls filled out and returned an identical questionnaire. Response options for each question were framed on a seven-point scale in which 7 represented best function and 1 represented worst function. Male-to-female ratio and mean age were similar to those of controls for the inflammatory bowel disease group. In each dimension, as well as globally, the quality of life of patients with inflammatory bowel disease was significantly worse than that for their age- and sex-matched controls. In conclusion, this survey demonstrates that inflammatory bowel disease adversely affects quality of life in a highly motivated group of "well" outpatients when compared to an age- and sex-matched population.     

Mutations in the retinal guanylate cyclase (RETGC-1) gene in dominant cone-rod dystrophy

The dominant cone-rod dystrophy gene CORD6 has previously been mapped to within an 8 cM interval on chromosome 17p12-p13. The retinal- specific guanylate cyclase gene (RETGC-1), which maps to within this genetic interval and previously was implicated in Leber's congenital amaurosis, was screened for mutations within this family and in a panel of small families and individuals with various cone and cone- rod dystrophy phenotypes. A missense mutation (E837D) was identified in affected members of the CORD6 family, as well as a second missense mutation (R838C) in three other families with dominant cone-rod dystrophy. RETGC-1 is only the fourth gene to be implicated in cone-rod dystrophy and this is the first report of dominant mutations in this gene.      

Measurement of total bile acids in gastric juice

An established method for the assay of total bile acids was validated for use in fasting and post-prandial gastric juice samples. Fasting and post-prandial intragastric bile acid concentrations were measured in 29 healthy volunteers, 15 patients after vagotomy and gastrojejunostomy (V and GJ) and 15 patients after vagotomy and pyloroplasty (V and P). Healthy female volunteers had higher post-prandial bile acid concentrations than age matched healthy males (p less than 0.02). Patients with V and GJ had higher fasting and post-prandial bile acid concentrations than age and sex matched control subjects (p less than 0.01). Patients with V and P had higher bile acid concentrations than control subjects only in post-prandial samples (p less than 0.05).