The ASCUS : SIL ratio and the reference laboratory pathologist.

The atypical squamous cells of undetermined significance (ASCUS) : squamous intraepithelial lesion (SIL) ratio was proposed to monitor laboratory use of the ASCUS diagnosis. This study addresses problems associated with comparing pathologists by this means. An intuitive example showed the ASCUS : SIL ratio depends on the prevalence of smears from patients who actually have SIL. In this study of 2000 cervical smears, each of five pathologists made 400 diagnoses. Differences among proportions of SIL diagnoses were statistically significant; differences among proportions of ASCUS diagnoses were not. Had an ASCUS : SIL ratio upper limit of 3.0 been used, two pathologists would have been misidentified as having high ASCUS diagnosis rates. Unlike the situation for laboratories, potential variability in SIL prevalence requires caution in the use of this ratio in assessing pathologists. An alternative measure that is independent of prevalence, the ASCUS : SIL odds ratio, is posited.

Sire marbling score expected progeny difference and weaning weight maternal expected progeny difference associations with age at first calving and calving interval in Angus beef cattle.

Field records from the American Angus Association were used to study the associations of sire marbling score EPD and sire weaning weight maternal (milk) EPD with age at first calving (AFC) and calving interval (CI). Cows were selected based on the accuracy of their sire's milk (> or =.7) or marbling (> or =.6) EPD. The data were screened using biological constraints, and regression models were used to identify records that were greater than 5 SD from the mean. The AFC was modeled for both milk and marbling data sets to account for effects of year, sire EPD, and their interaction. The CI was subdivided into first, second, and mature calving interval traits and modeled to account for state, year, calf sex, calf birth weight (BW), calf weaning weight (WW), sire EPD, and interactions of EPD with year and state. Derivative-free REML was used to estimate heritability and genetic correlations for AFC and CI. Sire milk EPD and marbling EPD were predictors of AFC (P < .001); however, pooled estimates were unreliable because of state x EPD interactions (P < .001). Increases in sire milk EPD resulted in reductions in AFC; however, there was no consistent pattern to effects of marbling EPD increases. Models accounted for < 8% of variation in AFC. Sire milk EPD was not a predictor of first, second, or mature CI (P > .1). Sire marbling score EPD was not a predictor of second, or mature CI (P > .1); however, it was associated (P = .059) with first CI, although regression estimates varied across states and prevented pooling. The BW, sex, and WW were predictors of CI (P < .001). Increases in BW resulted in longer mature CI, and mature CI decreased as WW increased. The AFC was heritable (.22), and CI traits had heritabilities ranging from .01 to .03. The AFC was genetically correlated with first CI (-.6) and mature CI (-.93). Genetic correlations between CI traits were uninterpretable because of low additive genetic variances. In conclusion, sire marbling score and milk EPD do not seem to be reliable predictors of AFC or CI. The BW and WW have significant but small effects on AFC and CI. Selection for AFC is possible, but earlier calving heifers may have longer calving intervals.

Minimum sample sizes for identifying chromosomal fragile sites from individuals: Monte Carlo estimation.

A Monte Carlo simulation procedure was used to estimate the exact level of the standardized X2 test statistic (Xs2) for randomness in the FSM methodology for the identification of fragile sites from chromosomal breakage data for single individuals. A random-number generator was used to simulate 10,000 chromosomal breakage data sets, each corresponding to the null hypothesis of no fragile sites for numbers of chromosomal breaks (n) from 1 to 2000 and at three levels of chromosomal band resolution (k). The reliability of the test was assessed by comparisons of the empirical and nominal alpha levels for each of the corresponding values of n and k. These analyses indicate that the sparse and discrete nature of chromosomal breakage data results in large and unpredictable discrepancies between the empirical and nominal alpha levels when fragile site identifications are based on small numbers of breaks (n < 0.5 k). With n > or = 0.5 k, the distribution of Xs2 appears to be stable and non-significant differences in the empirical and nominal alpha levels are generally obtained. These results are inherent to the nature of the data and are, therefore, relevant to any statistical model for the identification of fragile sites from chromosomal breakage data. For FSM identification of fragile sites at alpha = 0.05, we suggest that n > or = 0.5 k is the minimum reliable number of mapped chromosomal breaks per individual.

Determining the value of additional surrogate exposure data for improving the estimate of an odds ratio.

We consider the design of both cohort and case-control studies in which an initial ('stage 1') sample of complete data on an error-free disease indicator (D), a correct ('gold standard') dichotomous exposure measurement (X) and an error-prone exposure measurement (Z) are available. We calculate the amount of additional information on the odds ratio relating D to X that one can obtain from a second ('stage 2') sample of measurements only on D and Z. If one allows for differential measurement error in Z, there is often little advantage in having more than four times as much data in stage 2 data as in stage 1. With the assumption that a non-differential measurement error model is reasonable, larger amounts of stage 2 data can be useful. Simulations indicate that stage 1 samples of modest size (50 cases in case-control studies and 50 failures in cohort studies) yield sufficiently reliable estimates of needed parameters to assist in determining an appropriate size for the stage 2 sample. These ideas apply in settings either where the amount of stage 1 data is limited and fixed by external constraints or where one has gathered stage 1 data in advance to avoid collecting superfluous stage 2 data.

Identifying chromosomal fragile sites from individuals: a multinomial statistical model.

The inability to identify fragile sites from data for single individuals remains the major obstacle to determining whether these chromosomal loci are predisposed to cancer-causing and evolutionary rearrangements. We describe a novel statistical model that is amenable to data from single individuals and that establishes site-specific chromosomal breakage as nonrandom with respect to the distribution of total breakage. Our method tests incrementally smaller subsets of the data for homogeneity under a multinomial model that assigns equal probabilities to a maximal set of nonfragile sites and unrestricted probabilities to the remaining fragile sites with significantly higher numbers of breaks. We show how standardized Pearson's chi-square (X2) and likelihood-ratio (G2) statistics can be appropriately used to measure goodness-of-fit for sparse contingency (individual-based) data in this model. A sample application of this approach indicates extensive variation in fragile sites among individuals and marked differences in fragile-site inferences from pooled as opposed to per-individual data.

Problem-solving appraisal in suicide ideators and attempters.

The present study expands on previous research proposing a diathesis-stress-hopelessness model of suicidal behavior. The role of problem-solving appraisal within such a conceptual framework and the generalizability of the model across both suicide ideators and attempters are explored. Results support the critical role played by problem-solving appraisal in predicting both hopelessness and suicide ideation.

Diagnostic comorbidity in persons with suicidal ideation and behavior.

OBJECTIVE: An initial finding of heightened risk of suicidal ideation or behavior among individuals in a random community sample who met diagnostic criteria for panic disorder or panic attacks was not replicated in later studies of both general and specific groups of psychiatric outpatients. The present study represented another effort to validate the finding. METHOD: The participants included 209 outpatients who had attempted suicide or were at high risk for continued suicidal behavior or eventual suicide. All subjects were evaluated with a structured clinical interview for assigning DSM-III-R diagnoses, the Modified Scale for Suicidal Ideation, the suicidal ideation subscale of the Suicide Probability Scale, and the Beck Hopelessness Scale. RESULTS: The findings indicated the relative complexity and importance of diagnostic comorbidity among these suicidal subjects. Mood disorders were the most frequent primary diagnoses, followed by phobias, posttraumatic stress disorder (PTSD), generalized anxiety disorder, and panic disorder. Panic disorder was not present as an isolated, independent diagnosis; on the contrary, all of the patients with panic disorder also received at least one additional comorbid diagnosis. Mean scores for suicidal ideation and hopelessness were greatest for patients with current comorbid primary mood disorder and panic disorder. However, a critical and equally important role was played by comorbid PTSD, generalized anxiety disorder, and phobias. CONCLUSIONS: The findings represent another failure to validate, with a specific clinical group, panic disorder as an independent risk factor for suicidal ideation or behavior. However, they highlight the possibility that panic disorder and other anxiety disorders are risk factors when they co-occur with a primary mood disorder.

Performance of three tropical hair sheep breeds.

The performance of three hair sheep breeds (Brazilian Somali, Morada Nova, and Santa Ines) was evaluated in the production environment of northeastern Brazil. Data from a total of 524 lambs sired by 21 rams and out of 190 ewes were analyzed. These data were collected from 1980 to 1983 at Sobral, Brazil from an experiment designed to compare performance of the three breeds. The traits included weights of lambs at birth, weaning, 8 mo, 10 mo, and yearling ages and ewe characters of weight at lambing (EWT), total lamb weight born (LWB), total lamb weight weaned (LWW), and prolificacy rate (PR). Differences (P < .01) among breeds were found for all characters. The Brazilian Somali, the smallest and slowest-gaining breed, was less sensitive to yearly variation than were the other breeds. The Santa Ines, the largest and fastest-gaining breed, was superior in LWB and LWW per ewe lambing. Averaged over the 4-yr period, the Morada Nova had the highest PR (1.82), and the Brazilian Somali and Santa Ines had similar PR (1.39 and 1.31, respectively). Environmental effects on PR due to yearly rainfall quantity and distribution pattern influenced lamb growth up to weaning and ewe reproduction performance. Breed x year (P < .05) interaction effects on PR were largely attributable to the Somali breed's exhibiting higher PR than the Santa Ines and Morada Nova breeds during the relatively wet years of 1981 and 1982.

Characterization of relative growth of empty body and carcass components for bulls from a five-breed diallel.

Slaughter and carcass data were obtained on 197 bulls produced in a diallel involving Angus, Brahman, Hereford, Holstein and Jersey that were slaughtered at either 6, 9, 12, 15, 18, 24, or 30 mo of age. Bulls were given ad libitum access to a 72% TDN diet on an individual basis from 6 mo of age until slaughter. Empty body weight (EBWT) was determined as the sum of the weights of blood, hide, hard drop, soft drop (minus contents of the digestive tract), and carcass weight (CWT), which were recorded at slaughter. Carcass protein (CPROT) and fat (CFAT) were based on weights and chemical analyses of lean and fat tissue and bone of the carcass. Empty body protein (EBPROT) and fat (EBFAT) were based on weights and chemical estimates of the components of the empty body. Growth of EBWT, EBPROT, EBFAT, CWT, CPROT, and CFAT relative to either live weight (LWT), EBWT, or CWT were investigated using the allometric equation. Breed-type differences existed (P less than .01) for the growth of EBWT relative to LWT. Comparisons of general combining abilities revealed that Angus, Hereford, and Jersey generally had lower maturing rates of EBWT relative to LWT and that Brahman and Holstein had higher maturing rates. Across breed-type, relative growth rates indicated that fat and protein were later-maturing components relative to LWT, EBWT, or CWT, which implies that other components mature relatively earlier. Relative maturing rates of components studied were not important in explaining differences in body composition that have been previously reported for these breed-types.

Relationships between measures of feed efficiency and transmitting ability for milk of Holstein cows.

Feed efficiency measures, gross energy (solids-corrected milk/estimated energy intake) and nitrogen (milk nitrogen/nitrogen intake) utilization, and apparent digestibilities of ration dry matter, nitrogen, acid detergent fiber, and starch were calculated for 134 samples of 75 daughters of 31 Holstein sires. Cows were in 5- to 9-day nitrogen balance trials in first and second trimesters of lactation and were fed for ad libitum consumption corn silage-based complete rations formulated to meet average nutrient requirements. The objective was to test the hypothesis that feed efficiency diminishes as milk increases from selection. The sample of cows closely approximated the distribution of genetic ability for milk of the Holstein breed. Nonsiblings of same parity (one, two, three or more), calving within 2 wk of each other and differing by at least 140 kg estimated transmitting ability, were paired in nitrogen balance trials. Evidence for diminishing returns to increased transmitting ability for milk was nil for any measure of feed efficiency. Energy efficiency showed linear increases when regressed on cow transmitting ability for fat-corrected milk, but other measures of dietary utilization were unrelated to milk yield.