SOME STATISTICAL OBSERVATIONS ON A CO-OPERATIVE STUDY OF HUMAN PULMONARY PATHOLOGY

Observer variation in the histological diagnosis of plasmacytoid leukemia (marine anemia)

The reliability of past histological criteria for the diagnosis of plasmacytoid leukemia was investigated by studying observer variation in the diagnosis of the disease. Participants blindly evaluated a series of histological samples and classified them as positive, negative or questionable cases of the disease. Intra- and interpathologist agreement were used to assess reliability and were determined by calculating the observed agreement in diagnosis and the kappa statistic. There was poor overall agreement for the classification of sample cases. Questionable cases were most frequently misclassified but marked disagreement also existed for positive and negative samples. Access to historical information prior to histological examination influenced agreement. The results show that previously described histological criteria alone were insufficient for establishing the diagnosis of plasmacytoid leukemia.

External quality assessment of clinical laboratories in the United Kingdom

A review is given of the National External Quality Assessment Schemes (NEQASs) in various pathology disciplines in the United Kingdom, with a discussion of the relative roles of the DHSS, individual laboratory scientists, and the relevant professional bodies. Principles of operation and scientific problems in the design of NEQASs in different disciplines are described and contrasted, and some comparisons with the experience in other European countries and the USA are drawn.

Discrepancies in the histological diagnosis of hydatidiform mole

Sections of tissue from 256 patients on which a histological diagnosis of hydatidiform mole had been made were reviewed by a visiting pathologist. There was agreement between the reporting pathologists and the visiting pathologist in only 55.1 per cent of cases, a less severe diagnosis was made by the visiting pathologist in 42.2 per cent of cases. The disagreement was as high as 66.6 per cent with pathologists who rarely worked in the gynaecological field. This study casts serious doubt on the consistency of the histological diagnosis of hydatidiform mole made in any one laboratory and between different laboratories. It is suggested that in epidemiological studies the diagnosis should be made by a panel of pathologists using strict histological criteria and in an individual laboratory diagnosis should be made or confirmed by a pathologist experienced in gynaecological pathology.

Quality control in histopathology and diagnostic cytology

The need for quality control in diagnostic histopathology and cytology is analysed together with a discussion of previously reported experience in this field. The philosophical and mathematical inferences of this type of exercise are debated also in relationship to personally observed experiences in respect of uterine cervical cytology and histology. The desirability of methods of monitoring of diagnostic quality and of obtaining quality improvement are emphasized and suggestions made regarding the techniques most suited to these objectives.