Improved sensitivity of fuzzy logic based tumor marker profiles for diagnosis of pancreatic carcinoma versus benign pancreatic disease

BACKGROUND

The definite diagnosis of pancreatic tumors of unknown origin remains a clinical challenge. Imaging techniques may fail to differentiate malignant tumors from inflammation, especially in chronic pancreatitis. In a considerable number of cases, the definitive diagnosis needs laparotomy. Single tumor markers as CA 19-9 or CEA are of limited value in these cases because of their limited sensitivity and specificity. This study was performed to find out, whether a classification method based on fuzzy logic analysis of tumor marker profiles is feasible in patients with pancreatic carcinoma and benign pancreatic disease.

PATIENTS AND METHODS

Tumor markers and other clinical and laboratory parameters of 74 consecutive patients, either with histologically proved pancreatic carcinoma (n = 43) or presumed benign pancreatic disease (n = 31) assessed by ultrasound, endoscopic retrograde pancreatography, or computed tomography were analysed in order to detect their diagnostic value in the multi-dimensional approach of fuzzy logic analysis.

RESULTS

Given a specificity of 95%, sensitivity was considerably increased by the fuzzy logic method (83%) compared with the best single tumor marker CA 19-9 (65%). CA 19-9, CYFRA 21-1 and CA 15-3 gave the most considerable contributions to the classification system, whereas CEA, CA 125, CA 72-4, AFP, liver enzymes, lipase, amylase, bilirubin, and ferritin were of no or little value.

CONCLUSIONS

Tumor marker profiles analysed with the fuzzy logic method may have an improved sensitivity compared with single standard tumor markers. The diagnostic efficacy should be proved in patients with pancreatic tumors of unknown origin.

The mutant distribution of an RNA species replicated by Q beta replicase

The mutant spectrum of an RNA species that is replicated by Q beta replicase, MNV-11, was investigated by retrotranscribing the RNA to DNA and cloning it into plasmids. The sequences of several cDNA clones of MNV-11 populations amplified by Q beta replicase under various conditions were determined and compared. A surprisingly broad mutant distribution was found: the consensus sequence never made up more than 40% of the total population and was accompanied by many mutants. Most mutants had several base exchanges, insertions and/or deletions; up to nine of the total 86 nucleotides were changed. The mutants found had replication rates comparable to that of the wild-type and were thus enriched in the population by selection forces. When the growth conditions were changed, the mutant distribution centre was shifted. The published consensus sequence of MNV-11 did not have the highest growth rate of the mutants, but was rather the best adapted to the various selection forces governing the growth phases the replicating RNA went through, i.e. it had found an optimal compromise between the rates of overall replication, enzyme binding and double strand formation.

Colour and brightness components of foveal visual evoked potentials in man

The different effects of colour and brightness on the transient visual evoked potentials to a foveal stimulus have been investigated in a psycho-physically controlled stimulus set-up, in which equally bright red, orange and green stimuli were substituted for a standard yellow stimulus. These colour-evoked responses were compared with the responses to additional brightness increments and decrements of each of the colour stimuli. An initial component of small amplitude, P55, was followed by a colour-dominated component, N87, and a luminance-dominated component, P120, with a maximum at the occipital electrode. Both N87 and P120 showed a decline in amplitude at the parietal electrode and P120 had a reversed polarity at FZ. These results indicate that the responses to equally bright green and red stimuli have closely similar wave forms, but that this changes rapidly with additional brightness differences. Comparison with the reports of subdural recording of colour-evoked potentials in the macaque striate cortex suggests that P55 corresponds with the primary excitation via geniculo-cortical fibres and that N87 and P120 represent later stages of cortical processing.

Course of disturbance of EOG in retinal vessel occlusions

More than 60 patients with retinal vessel occlusions were examined using the electro-oculogram (EOG) ramp test. In the course of the disease a systematic disturbance of the slow oscillation of the corneoretinal potential occurred. First, the latency of the light peak increased. Then the peak decreased and was reached up to 5 min later than in the healthy eye. In the final stage the basic level dropped to about half of the normal value and light response was absent. During the next few weeks an improvement in the basic level took place, but usually this did not involve improved vision.

Correlation between the c wave and the corneoretinal potential in man

In the human DC-ERG the amplitude of the slow negative potential is modulated by the corneoretinal potential as well as the c wave. Depending on the phase of the slow oscillation of the corneoretinal potential some subjects show a c wave and others do not. Some subjects, who show a c wave during the maximum of the slow oscillation, have no c wave during the minimum, but show the slow negative potential. A hypothesis of slow oscillation influence on the c wave is given.

Examination of the fast oscillation of the corneoretinal potential under clinical conditions

The "fast oscillation" of the corneoretinal potential can be precisely examined by means of cyclic light stimuli and an automatic measuring device. This new procedure is carried out during the period of adaptation as part of the usual EOG-test. Normal values and some clinical findings are presented. The fast oscillation may provide additional information when compared with EOG and ERG results.

EOG: light test and dark test

The EOG test is divided into two parts: a light and a dark test. The adaptation period is extended to 30 min. During this adaptation period the luminance in the cabin decreases (or increases) slowly to the starting value of the light or dark step. In a model, we studied the influence of this ramplike luminance course on the results. Standard values for the test were calculated with 30 test persons. Our test results show a lower relative standard deviation (V = 10%) compared with earlier published results.

ERG of humans without C-wave

Three out of 18 healthy persons investigated with the DC-ERG do not show a c-wave. By varying the adaptation levels and intensities of the stimuli four components in the human ERG can be isolated, the cone and rod late receptor potentials, the positive DC response, and a c-wave in most subjects. It is suggested that investigation of these components reveals a more detailed understanding of the pathophysiologic mechanisms in some retinal diseases.

Experiments concerning the human C-wave

The dependence of the human c-wave from the step amplitude was studied qualitatively. The maximum of the c-wave is achieved with light stimuli longer than 10 sec. After a dark period of 10 sec a fully developed c-wave appears. Also, in response to a brilliant photoflash a c-wave could be recorded. The influence of a mobile pupil on the response in the DC-ERG is demonstrated. Responses of the retinal potential to square wave and sinusoidal stimuli of different period times have been registered.

A method for DC-ERG recording of alert humans

We developed a technique for DC-coupled ERG recording of the alert human. The equipment consists of three units: a new cornea suction glass, a separate electrode, and a vacuum control device. We get stable recordings of more than one-half hour. By comparison with the EOG the identity of the EOG "on"-peak and ERG c-wave is assured. A fine structure of DC-ERG recording of 100 muV amplitude is closely correlated to the variation of the blood pressure in the ophthalmic artery. It may either be caused by the variable electric conductivity of the eyeball due to the blood pressure or it may reflect a variation of the retinal potential itself.