Mechanical strength vs. degradation of a biologically-derived surgical mesh over time in a rodent full thickness abdominal wall defect.

The use of synthetic surgical mesh materials has been shown to decrease the incidence of hernia recurrence, but can be associated with undesirable effects such as infection, chronic discomfort, and adhesion to viscera. Surgical meshes composed of extracellular matrix (i.e., biologically-derived mesh) are an alternative to synthetic meshes and can reduce some of these undesirable effects but are less frequently used due to greater cost and perceived inadequate strength as the mesh material degrades and is replaced by host tissue. The present study assessed the temporal association between mechanical properties and degradation of biologic mesh composed of urinary bladder matrix (UBM) in a rodent model of full thickness abdominal wall defect. Mesh degradation was evaluated for non-chemically crosslinked scaffolds with the use of (14)C-radiolabeled UBM. UBM biologic mesh was 50% degraded by 26 days and was completely degraded by 90 days. The mechanical properties of the UBM biologic mesh showed a rapid initial decrease in strength and modulus that was not proportionately associated with its degradation as measured by (14)C. The loss of strength and modulus was followed by a gradual increase in these values that was associated with the deposition of new, host derived connective tissue. The strength and modulus values were comparable to or greater than those of the native abdominal wall at all time points.

Adjusting for regression effect in uncontrolled studies.

When clinical studies require enrolled patients to have abnormal assays, the natural tendency of repeat measurements to regress toward the mean can lead to a false assessment of effectiveness of therapy. We propose a method to more accurately estimate the true effect of therapy by adjusting for a component of improvement that can be attributed to regression effect. The model we use allows for a combination of additive and/or multiplicative effects of the therapy.

A robust method for the analysis of experiments with ordered treatment levels.

A robust approach for the analysis of experiments with ordered treatment levels is presented as an alternative to existing approaches such as the parametric Abelson-Tukey test for monotone alternatives and the nonparametric Terpstra-Jonckheere test. The method integrates the familiar Spearman rank-order correlation with bootstrap routines to provide magnitude of association measures, p values, and confidence intervals for magnitude of association measures. The advantages of this method relative to five alternative approaches are pointed out.

Testing for the antiphospholipid syndrome: importance of IgA anti-beta 2-glycoprotein I.

BACKGROUND: Testing for the antiphospholipid syndrome (APS) using anticardiolipin antibodies (aCL) has been problematic. Titers may fluctuate or even become negative. Anti-beta 2-glycoprotein I assays (abeta2-GPI) may be more reliable for diagnosis. METHODS: In a prospective, blinded study over a nine-month period we retested all patients seen for routine follow-up visits in our clinic who had previously been evaluated for aCL-associated illnesses. Patients were stratified into two groups: group A-patients previously positive for aCL; group B-patients previously negative for aCL. Both groups were further classified according to disease severity. Patients were retested for both aCL and abeta2-GPI (isotypes G, M, A for each) using uniform testing standards. RESULTS: 118 patients with previously positive aCL (group A) were retested. Repeat aCL were positive in 52/118 (44%), abeta2-GPI positive in 69/118 (58%) and 82/118 (69.5%) were positive for one or both assays. In patients with serious organ damage (92% with documented APS), 48.6% were aCL positive, 64% positive for abeta2-GPI, and 75.7% were positive for one or both assays. When only one assay was positive, abeta2-GPI was most frequent (P=0.0096). Overall, IgA abeta2-GPI was the most frequent isotype found (60.9%). On retesting of 73 aCL-negative patients (group B), 9/73 (12%) were aCL positive, 27/73 (36%) were abeta2-GPI positive, with 24/73 (32.9%) having isolated abeta2-GPI. Of those positive for abeta2-GPI, IgA abeta2-GPI was present in 74. 1%. Many of these patients had documented APS. CONCLUSION: Based on our data, abeta2-GPI assays are superior to aCL assays for diagnosis of APS. The combined use of both assays enhance positive testing results in up to 75% of patients with APS at any stage of illness. ACL negative patients suspected of having APS should be retested for both abeta2-GPI and aCL. IgA abeta2-GPI appears to be the most important isotype detected.