Engineering in software testing: statistical testing based on a usage model applied to medical device development.

When a population is too large for exhaustive study, as is the case for all possible uses of a software system, a statistically correct sample must be drawn as a basis for inferences about the population. A Markov chain usage model is an engineering formalism that represents the population of possible uses for which a product is to be tested. In statistical testing of software based on a Markov chain usage model, the rich body of analytical results available for Markov chains provides numerous insights that can be used in both product development and test planing. A usage model is based on specifications rather than code, so insights that result from model building can inform product decisions in the early stages of a project when the opportunity to prevent problems is the greatest. Statistical testing based on a usage model provides a sound scientific basis for quantifying the reliability of software.

Prevalence and recognition of panic states in STARNET patients presenting with chest pain.

BACKGROUND: The purpose of this study was to document the prevalence of panic states in patients presenting with chest pain in primary care settings, to determine the recognition rate of panic states by family physicians, and to assess the impact of lack of recognition on interventions and costs. METHODS: Patients from the South Texas Ambulatory Research Network (STARNET) presenting with a new complaint of chest pain were asked to participate in the study. Before seeing their physician, subjects completed the panic disorder section of the Structured Clinical Interview (SCID) of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised. The SCID was used to assign diagnoses of panic disorder, infrequent panic, or limited symptom attacks. Health care outcomes included medications prescribed, tests ordered, follow-up and referrals, costs, and physician diagnosis. RESULTS: Although approximately one half of the 51 patients in this study met criteria for either panic disorder or infrequent panic, few were recognized by physicians as having a panic state (kappa = -.003). Patients with panic disorder were more likely to receive follow-up or referral (P = .042), incurring higher follow-up costs (P = .080). Patients with infrequent panic received more testing (P = .008), with higher costs for testing (P = .001) and higher overall costs (P = .067). Panic-diagnosis associations were found between psychotropic (P = .001) and total (P = .070) medications as well as follow-up and referral costs (P = .009). CONCLUSIONS: Although common, panic states are rarely recognized in patients presenting with complaints of chest pain. The presence of panic leads to more testing, follow-up, and referral with subsequent higher costs. Failure to diagnose panic results in increased prescribing of medications, higher costs, and inappropriate pharmacotherapy.

A rapid procedure for routine double staining of cartilage and bone in fetal and adult animals.

A simple, rapid procedure for dual staining of cartilage and bone in rodents, particularly in late gestation, has been developed for routine use. The procedure involves rapid, complete skinning of fresh eviscerated specimens following a 30 sec immersion in a 70 C water bath. The unfixed specimen is stained in a mixture of 0.14% Alcian blue and 0.12% alizarin red S in ethanol and glacial acetic acid. Specimens are then macerated in 2% KOH, cleared and hardened in 1:1 glycerin and distilled water, and stored in pure glycerin. Rapid staining of cartilage only is done in a mixture of 0.08% Alcian blue, glacial acetic acid, and ethanol, with subsequent maceration, clearing, and hardening as in the double staining procedure. Rapid staining of bone only, concurrent with maceration of soft tissue, can be done by placing fresh, unskinned specimens in a diluted mixture of alizarin red S in 2% KOH, with subsequent clearing and hardening in 1:1 distilled water and glycerin. Good quality fetal specimens can be prepared for examination by any of these procedures in a minimum of 11/2-2 days as compared to a minimum of 4-5 days for other procedures. Double stained specimens can be examined for abnormalities of the cartilage as well as bone.