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Biomedical subjects

W Schaafsma

Publications and source records attributed to W Schaafsma.

8 recordsLinked to original sources
PubMed1997

Which cytological criteria are the most discriminative to distinguish carcinoma, lymphoma, and soft-tissue sarcoma? A probabilistic approach.

The reliability of fine-needle aspiration cytology (FNA) for distinguishing between carcinoma, lymphoma, and sarcoma was established in a previous study (Thunnissen et al., Cytopathology 1993; 4:107-114). The purpose of this study was to investigate which criteria were useful for a probabilistic diagnosis. A total of 78 randomly chosen FNA smears (31 carcinomas, 24 lymphomas, and 23 sarcomas) was sent around and read "blindly" by six cytopathologists. Each pathologist completed a list of 16 criteria for every case. Histology was used as a reference standard. A statistical analysis led to the selection of three criteria: "lymphoglandular bodies," "well-defined clusters," and "spindle-cell nuclei," associated with lymphoma, carcinoma, and soft-tissue sarcoma, respectively. Given the scores on these criteria, the probabilities to be assigned to the three diagnostic categories can be read from a table. It turns out, as one might expect, that the classification of the most probable disease is pretty reliable if one cytologic criterion scores much higher than the other two criteria. On other cases, fuzziness appears and misclassifications are far from improbable. This study offers a general cytologic approach. The cytologic criteria "lymphoglandular bodies," "well-defined clusters," and "spindle-cell nuclei" can be used both in daily practice and in education to assign posterior probabilities to carcinoma, lymphoma, and soft-tissue sarcoma.

Biopsy, Needle↗
PubMed1992

Further evaluation of quantitative nuclear image features for classification of lung carcinomas.

The usefulness of quantitative nuclear image features (QNI) for the histological classification of lung carcinomas was investigated. As no clear distinction could be established between the distributions of these features for the nuclei of squamous cell, adenocarcinoma, and large cell carcinoma, the attention was restricted to the discrimination between small cell lung carcinoma (SCLC) and non-small cell carcinoma (NSCLC). This discrimination is the crucial one in discussions about the choice of treatment. The differences between SCLC and NSCLC are statistically highly significant for various QNI features. The use of more than one QNI feature hardly raised the discriminatory performance with respect to the distinction between SCLC and NSCLC. Inferences were made about the probability and confidence interval of SCLC for a given QNI feature. It is concluded that in cases of uncertainty or disagreement, nuclear characteristics are useful for the discrimination between SCLC and NSCLC.

Adenocarcinoma↗
PubMed1991

[The effect of thymectomy in patients with myasthenia gravis without thymoma; a statistical analysis].

In order to determine the effect of thymectomy on the prognosis of patients with myasthenia gravis, an analytical-descriptive study was carried out in the Neurological Clinic of the Groningen University Hospital and the Mathematical Institute of Groningen University. In 183 patients with generalized myasthenia gravis without thymoma, with onset between 9 and 46 years of age, the severity of the disease was scored by one neurologist at fixed times (0.5, 1, 2, 3, etcetera up to 15 years) after onset. Thymectomy was performed in 144 patients at different times (0.5, 1, 2, 3, etcetera up to 7 years) after onset. Logistic regression analysis was carried out with, as the criterion for marked improvement, a decrease of the disease score by 50%. Using this criterion, age, sex, duration of the disease and severity of the disease prior to operation played no distinct parts as prognostic factors. At different periods after the onset of the disease, groups of patients operated or not (yet) operated were compared. Patients subjected to thymectomy within 5 years after onset of myasthenia gravis had a better probability of halving of the severity score than patients not subjected to operation. These data render it possible in the individual patient to make an adequate estimate of the probability of marked improvement if thymectomy is performed or postponed.

Adolescent↗
PubMed1989

Reference values of anthropometric measurements in Dutch children. The Oosterwolde Study.

In the period 1979-1980 the following anthropometric measurements were recorded in 2351 healthy Dutch children from 0-17 years of age: height, weight, sitting height, arm span, lengths of upper-arm, lower-arm and hand, tibial length, foot length, biacromial diameter, biiliacal diameter, and head circumference. Corresponding percentile values were constructed on the basis of normality assumptions, the mean and standard deviation at age t being determined by a cubic spline approximation. The results are compared with other studies and given in the form of growth charts.

Adolescent↗
PubMed1987

Determining nucleolar multiplicity and cell number from sectional data.

The occurrence of more than one nucleolus within the cellular nucleus (polynucleolarity) is a well-known phenomenon during the proliferative cell cycle, both under normal and pathological conditions (e.g. neoplasia). It can also be observed in neuronal nuclei at early stages of their maturation. Polynucleolarity merits investigation for cytological reasons. In an histological section, the observed number of nucleoli in a nucleus may be smaller than the actual number. In order to estimate the true distribution of the number of nucleoli per nucleus from the observed distribution, the mathematical relation between these distributions is derived on the basis of rather restrictive stereological assumptions. It is indicated how these distributions can be estimated from the data available and how the statistical uncertainties involved can be expressed. This paper arose from making cell counts. Two methods may be applied: all visible nuclear profiles are counted, nuclear profiles are only included if at least one nucleolus is visible in the section. We recommended a combination of these two methods. An advantage of our theory for determining cell number is that one can often manage without the rather restrictive stereological assumptions needed hitherto. The advantage of expressing statistical uncertainties in estimated nucleolar multiplicity probabilities and cell numbers is indicated.

Animals↗
PubMed1986

Toward individual prognosis of IgA nephropathy.

The individual prognosis of adult IgA nephropathy patients was studied using the proportional hazards model for the time from biopsy until endstage renal disease. After selection of the most relevant prognostic factors, the 75 patients were stratified with respect to hypertension and its treatment. In these strata, individual prognosis was based on the initial age-adjusted glomerular filtration rate, the initial proteinuria, the presence/absence of gross hematuria, and the presence/absence of microscopic hematuria. Using the scores of a patient on these variables, the probability of surviving any given period of time can be estimated either graphically or by calculation. Prediction is feasible up to about 10 years. Attention has been given to supply all relevant estimates with confidence limits. For each patient the estimated 5-year survival probability as predicted by the model was compared with the actual outcome.

Adult↗
PubMed1985

Smoothing techniques for obtaining reference values for measurements of children.

Constructing reference values for measurements of children, e.g. the mean height as function of age, one needs a smoothing technique. Various techniques will be discussed and applied to a particular study of anthropometric growth. The overall conclusion is that reliable curves can be obtained by using computer programs based on approximations by cubic splines, and by using the eye for choosing from the corresponding outputs.

Adolescent↗