False-positive Results In Patients Research Articles

Diagnostic strategies in osteomyelitis

Technetium-99 ( 99Tc) pyrophosphate bone scanning often identifies patients with osteomyelitis before roentgenographic findings appear. However, recent studies have shown that 99Tc bone scanning often gives false-negative results, especially in neonates. The accuracy of computed tomographic scanning and indium-111 leukocyte scanning for diagnosis of early osteomyelitis has not been established. 99Tc bone scanning often gives false-positive results in patients with other conditions leading to bone injury and repair, such as trauma or recent surgery, further limiting the usefulness of this Imaging procedure. Newer Imaging techniques have not been adequately evaluated to establish their specificity. Because of their high cost and unproved accuracy, these new Imaging procedures should not be routinely applied until their usefulness has been established. Bone biopsy remains the procedure of choice for establishing the diagnosis in patients suspected clinically to have osteomyelitis with negative findings on roentgenography and 99Tc bone scanning. Although Staphylococcus aureus is the leading cause of osteomyelitis, other pathogens cause 30 to 40 percent of cases. Aspiration or biopsy of the involved bone is usually required to choose appropriate antibiotic therapy. Bone biopsy is essential in chronic osteomyelitis, since cultures of sinus drainage are unreliable. Osteomyelitis in diabetics With foot infection and in association with decubitus ulcers presents special problems. Radionuclide scanning often give false-positive results in these patients. Proper diagnosis usually requires careful assessment of clinical and roentgenographic findings. Although bone biopsy seems useful in diagnosing osteomyelitis underlying decubitus ulcers, its role In diabetic patients with foot Infections is not established. I do not recommend biopsy of foot bones in diabetic patients, since culture of bone biopsy specimens often give unreliable results in these situations because of contamination with ulcer organisms.

The diagnosis of angina pectoris

The diagnosis of angina pectoris is dependent upon the history and electrocardiographic changes. It should be emphasized that electrocardiographic changes must be interpreted with a knowledge of the clinical history, so that the significance of suggestive changes is more apparent. The difficulty experienced by the patient with angina is characterized as a distress or discomfort, and not a pain. The discomfort is provoked by exertion, digestion, excitement, and emotion, and is classically located in the retrosternal area, with radiation to the inner aspect of the left arm, the hypothenar eminence, and the fourth and fifth fingers. The distress may radiate to the neck, the right arm, and the jaw, and may occur in only a segment of the distribution. It develops gradually over a period of 10 seconds to 2 minutes and is relieved promptly by rest or nitroglycerin. It may also be relieved by carotid sinus massage. It is usually wise to perform a double two-step Master's test, with the test discontinued if the patient develops discomfort. Positive electrocardiographic changes after exercise include: (1) right-angle S-T segment depression of 0.5 mm. or more, (2) S-T segment elevation, (3) bundle branch block, (4) inverted T waves becoming upright, and (5) T waves increasing 5 mm. or 300 per cent in amplitude, or inverted U waves. These changes are also significant if they occur spontaneously during the period of anginal distress. Suggestive electrocardiographic changes after exercise are: (1) arrhythmias, (2) inverted T waves with or without exercise, especially if the inversion is more than 2 mm., (3) postextrasystolic T-wave change with or without exercise, and (4) junctional S-T segment depression greater than 2 mm. Negative and false-positive changes after exercise include: (1) junctional S-T segment depression of less than 2 mm., (2) T of P depression, (3) inverted T waves less than 2 mm. with or without exercise, (4) autonomic changes, and (5) falsepositive results in patients with hypertrophy, bundle branch block, Wolff-Parkinson-White syndrome, after digitalization, or pericarditis. A double Master's exercise test was analyzed in 350 patients with normal resting electrocardiograms. One hundred and ninety had a definite history of angina, with positive changes in 57.9 per cent, suggestive changes in 14.2 per cent, and negative changes in 27.9 per cent. One hundred and sixty had a negative history, with positive changes in only 4.4 per cent, suggestive in 1.2 per cent, and negative in 94.4 per cent. Of 14 patients with coronary disease and inverted T waves in the control tracing, 2 had right-angle S-T depression, in 9 the T waves became upright, and in 3 there was no change. With improving methods of therapy, correct and early diagnosis is essential in the proper management of the patient with angina pectoris.

Accurate pregnancy testing in tranquilized patients.

The reported occurrence of false-positive results of pregnancy tests in patients taking certain tranquilizers has been investigated. The test in question involved the intra-abdominal injection of a urine concentrate from the patient into male frogs, and the production of spermaturia constituted a positive result. The 50 psychiatric patients in the present study were all receiving promazine, prochlorperazine, or perphenazine daily in substantial doses. Samples of serum were obtained for use in place of urine concentrates. Hyaluronidase was injected with the serum to facilitate adsorption. Two frogs weighing from 25 to 50 Gm. were used for each of the 50 tests. There was no evidence that the test carried out in this way would give false-positive results in patients receiving tranquilizers of the phenothiazine group.