Rate Of False-negative Results Research Articles

Impact of Proficiency Testing on Results of the Microscopic Agglutination Test for Diagnosis of Leptospirosis

A proficiency testing scheme for the leptospirosis microscopic agglutination test was provided to 37 laboratories in 23 countries in 2002 (round 1) and to 60 laboratories in 34 countries in 2003 (round 2). Thirty-four laboratories participated in both rounds. Each panel consisted of five rabbit serum samples, four of which were antisera raised against pathogenic serovars of Leptospira. One of these samples was a mixture of two different antisera. The rates of false-negative results, calculated on the basis of the assumption that serovars within a serogroup will cross-react, were 11% for round 1 and 14% for round 2. There were regional differences in the rates of false-negative results. The titers reported by laboratories testing for the same sample with the same serovar varied widely. Laboratories that had previously participated in round 1 reported fewer false-negative results in round 2 than new participants (10 and 21%, respectively [P = 0.002]) and reported 0.56 false-negative results per participant, whereas new participants reported 1.23 false-negative results per participant (P = 0.041). Laboratories that had previously participated also reported fewer false-negative results in round 2 than in round 1 when samples common to both rounds were tested (5 and 15%, respectively [P = 0.028]). The titers reported by the new participants were, on average, lower than those reported by the laboratories that had participated previously (P = 0.019) and were significantly more variable (P = 0.001). Analysis of these results suggests a positive impact of proficiency testing on the testing performance of the participating laboratories.

Cerebral blood oxygenation after cerebrospinal fluid removal in hydrocephalus measured by near infrared spectroscopy

Background The cerebrospinal fluid (CSF) tap test has been used for the diagnosis of chronic hydrocephalus to identify the candidates for surgical CSF shunting. However, a high rate of false negative results limits it utility. The purpose of this study is to investigate whether the concomitant monitoring of cerebral hemodynamics by near infrared spectroscopy (NIRS) can improve the diagnostic accuracy of the tap test. Methods Thirteen patients with dilated ventricular system were candidates for this study. We assessed for the patterns of cerebral blood oxygenation (CBO) change in hydrocephalus to determine whether CBO change after CSF removal is useful for selecting shunt candidates. Results Patients who showed clinical improvement following CSF shunting had a characteristic CBO change with increases in the concentration of oxyhemoglobin (Oxy-Hb), and patients without improvement during continuous CSF drainage test showed no increase in Oxy-Hb. Conclusion The current data suggests that CBF increases after CSF removal in hydrocephalus. Although the patients utilized in the present study had secondary chronic hydrocephalus, we speculate that these data could be applied to patients with idiopathic chronic hydrocephalus. Further investigation would be of benefit.

Enhancement of scFv fragment reactivity with target antigens in binding assays following mixing with anti-tag monoclonal antibodies

The phage display Ab library technology has been found to be a useful method to isolate antigen-specific Ab fragments, since the repertoire of antibody specificities is broad and since it bypasses the need of immunization. However, when screening clones isolated from a phage display Ab library, the yield of isolating antigen-specific Ab fragments is low and the rate of false negative results is high. This limitation reflects the low affinity/avidity of Ab fragments and/or the low density of the target antigen. To facilitate the isolation of Ab fragments with a broad range of affinities to antigens of interest from phage display Ab libraries, we have developed a simple method to increase the sensitivity of binding assays to detect the reactivity of single-chain fragments of antibody variable regions (scFv) with target antigens. This method involves the mixing of scFv fragments, expressing a c-myc epitope tag, with anti-tag mAb 9E10 prior to their use in binding assays in order to form stable dimeric Ab fragment–anti-tag mAb complexes. The increase in the reactivity of scFv fragments with the corresponding antigen is observed over a broad range of scFv fragment (6–800 μg/ml) and mAb 9E10 (0.5–30 μg/ml) concentrations, thereby facilitating the testing of scFv fragment preparations with unknown scFv fragment concentrations. Use of this method in binding assays resulted in a twofold increase in the reactivity of low-affinity purified scFv fragments with the corresponding antigen. Moreover, application of this method to screen clones isolated from phage display scFv libraries resulted in a reproducible increase in both the yield of antigen-specific scFv clones and the titer of scFv fragment preparations by a factor of 5 and 2- to 32-fold, respectively. Lastly, this method can be applied in both ELISA and flow cytometry and is independent of the characteristics of the antigen (i.e. whole cells, carbohydrates and purified protein) and/or of the library (synthetic scFv Library (#1), a large semi-synthetic phage display scFv library and the human synthetic VH+VL scFv library (Griffin.1 library)) used. Therefore, the method we have described represents a sensitive, simple and reproducible technique that will facilitate the isolation and use of scFv fragments.

Testing for the presence of disease by pooling samples

SummaryScreening of pooled urine samples was suggested during the Second World War as a method of detecting syphilis in US soldiers. Recently, pooling has been used in screening blood for Human Immunodeficiency Virus (HIV) antibody to help curb the further spread of the deadly virus. Pooling reduces the cost and also reduces the rates of false‐negative results in samples that are not disease‐free, a factor that has led to pooling not being adopted as an efficient procedure for screening HIV. This paper generalizes a common pooling strategy with retesting, and discusses its characteristics. Furthermore, it suggests a new testing strategy with retesting.

Radial tears of the posterior horn of the medial meniscus

Purpose: The purpose of this study was to introduce clinical features and characteristics of radial tears of the posterior horn of the medial meniscus and the results of arthroscopic surgery. Type of Study: Retrospective case series. Methods: From August 1996 to December 1999, 345 consecutive cases of medial meniscal tears were treated using arthroscopic surgery in Asan Medical Center, Seoul, Korea. Of these, 96 cases (27.8%) with radial tears of the posterior horn of the medial meniscus were reviewed. All patients were treated with arthroscopic partial meniscectomy. Based on medical records, including surgical notes and detailed arthroscopic photographs, we reviewed the age distribution of the patients, preoperative physical signs, magnetic resonance imaging, surgical findings, and clinical results using the Lysholm Knee Scoring scale and our own questionnaire. Results: Radial tears of the posterior horn of the medial meniscus were more common than previously known and also were more common in elderly patients. Most patients presented mechanical symptoms. Magnetic resonance imaging often failed to reveal the tears. Careful attention to the nature of pain and the physical examination was critical in making a diagnosis. Although most patients were elderly and had degenerated articular cartilages, subjective symptoms improved significantly after arthroscopic partial meniscectomy. Conclusions: Radial tears of the medial meniscus posterior horn are common. Diagnosis of this tear is often difficult because most patients have osteoarthritic knees masking meniscal tears and magnetic resonance imaging shows unacceptably high rates of false-negative results. Following strict surgical indications, arthroscopic partial meniscectomy can help patients with low morbidity. Level of Evidence: Level IV therapeutic study (case series, no or historical control group).

Cytologic Criteria of Cystic Papillary Carcinoma of the Thyroid

To establish differential cytologic criteria between benign and malignant thyroid cysts. The study was a retrospective, transverse, analytic, comparative one of 3 groups of patients with nonfunctional thyroid nodules subjected to fine needle aspiration biopsy (FNAB) and surgical resection of the lesions, with histologic study as the diagnostic gold standard. Fifteen cases of cystic papillary carcinomas (group 1) with initial false negative diagnoses, 42 goiters accompanied by cystic degeneration (group 2) and 15 noncystic papillary carcinomas (group 3) were studied. Independent variables were age and sex; dependent variables were the presence of tridimensional fragments, papillae, anisonucleosis, nuclear bars, pseudoinclusions, powdery chromatin, cytoplasmic vacuoles, metaplastic cytoplasm, psammoma bodies, autolysis, multinucleated giant cells, spindle cells, colloid, monolayered laminae and macrophages in FNAB specimens. Statistical analysis was performed by central tendency measures and the chi 2 test. The chi 2 test revealed a statistically significant difference between group 2 and the groups with papillary carcinoma based on the presence of tridimensional fragments, anisonucleosis, nuclear bars, pseudoinclusions, powdery chromatin, cytoplasmic vacuoles, metaplastic cytoplasm and autolysis. The above cytologic characteristics must be searched for systematically in the FNAB of every cystic lesion of the thyroid to rule out the presence of cystic papillary thyroid carcinoma and to decrease the rate of false negative results.

The polaroid suppression test in a pediatric population with ophthalmologic disorders.

The Polaroid suppression test (PST) is a new method for early detection of amblyogenic factors by screening for suppression. The apparatus can elicit suppression with the use of Polaroid filters. The aim of the present study was to examine a population of children with known ophthalmologic disorders using the PST to determine the rate of false-negative results of the PST. Six hundred four children, varying in age between 3 and 15 years (mean, 7.9) were examined using the PST. Ophthalmologic disorders ranged from strabismus and amblyopia to refractive disorders. Mean testing time for the PST was 43 seconds. The PST could not be administered to 34 children (5.6%); 443 children (73.3%) had abnormal results; and 127 children (22.2%) showed no suppression. The suppression in constant strabismus was detected in almost all cases. The sensitivity for accommodative forms of strabismus was lower, but amblyopia was never missed in these cases. In children with normal eye alignment, only 2.7% with an interocular acuity difference of more than 0.1 logMAR had no suppression. Of all 119 children with clinical defined amblyopia, only 1 (0.8%) did not have suppression. Overall sensitivity of the PST for strabismus and/or abnormal interocular acuity difference was 96.2% and specificity was 41.1%. The PST has great potential as a visual screening tool in young children. Only few children with amblyogenic factors were missed. Thus, the test can differentiate those children at risk for amblyopia from normally sighted children. Because specificity is lower, all children showing suppression with the PST in a screening situation should have further examination by the health care worker before being referred to the ophthalmologist.

The polaroid suppression test in a pediatric population with ophthalmologic disorders

Purpose The Polaroid suppression test (PST) is a new method for early detection of amblyogenic factors by screening for suppression. The apparatus can elicit suppression with the use of Polaroid filters. The aim of the present study was to examine a population of children with known ophthalmologic disorders using the PST to determine the rate of false-negative results of the PST. Methods Six hundred four children, varying in age between 3 and 15 years (mean, 7.9) were examined using the PST. Ophthalmologic disorders ranged from strabismus and amblyopia to refractive disorders. Results Mean testing time for the PST was 43 seconds. The PST could not be administered to 34 children (5.6%); 443 children (73.3%) had abnormal results; and 127 children (22.2%) showed no suppression. The suppression in constant strabismus was detected in almost all cases. The sensitivity for accommodative forms of strabismus was lower, but amblyopia was never missed in these cases. In children with normal eye alignment, only 2.7% with an interocular acuity difference of more than 0.1 logMAR had no suppression. Of all 119 children with clinical defined amblyopia, only 1 (0.8%) did not have suppression. Overall sensitivity of the PST for strabismus and/or abnormal interocular acuity difference was 96.2% and specificity was 41.1%. Conclusions The PST has great potential as a visual screening tool in young children. Only few children with amblyogenic factors were missed. Thus, the test can differentiate those children at risk for amblyopia from normally sighted children. Because specificity is lower, all children showing suppression with the PST in a screening situation should have further examination by the health care worker before being referred to the ophthalmologist.

Clinical evaluation of a new thyroglobulin immunoradiometric assay in the follow-up of differentiated thyroid carcinoma

Formal and clinical comparison of a new 3 (rd) -generation-Tg-IRMA (3-G-IRMA; Dynotest Tg-plus) with a conventional Tg-IRMA (3-G-IRMA; SELco Tg-assay) for patients with differentiated thyroid carcinoma. In addition we evaluated, if thyroglobulin (Tg) levels above a specific threshold concentration indicate the need for further investigations for residual disease. Tg concentration of 105 sera of 93 consecutive patients with a differentiated thyroid cancer was determined with both assays and compared at different cut-off values (Dynotest Tg-plus: 0.2, 1, 2 ng/ml; SELco Tg-assay: 0.5, 1, 2 ng/ml) with the clinical results in respect to the corresponding TSH concentration. Tg concentration did not show any significant difference (SELco Tg-assay 0.5 ng/ml, Dynotest Tg-plus 0.2 ng/ml). The Tg-values of both assays correlated with 97%. However, correlation of recovery in both assays was small (40%). The sensitivities and specificities of both assays at different cut-offs and TSH values did not reveal significant differences. In patients with TSH concentration > 30 micro U/ml the functional assay sensitivity was superior to arbitrary cut-offs in the decision to start further evaluations. In our study neither formal nor clinical significant differences between two Tg-assays were found. In a hypothyroid patient (TSH > 30 micro U/ml, Tg concentration exceeding the functional assay sensitivity) further investigations for residual disease are warranted. Higher thresholds are of limited value, due to an unacceptably high rate of false negative results.

Efficiency of a video-autorefractometer used as a screening device for amblyogenic factors.

High ametropia is known as a risk factor in developing amblyopia. The aim of the study was to evaluate the efficiency of a commercially available infrared videorefractometer (PowerRefractor) in examining children, and to evaluate its effectiveness in detecting amblyogenic factors of the refraction. The influence of cycloplegia was of interest. A total of 255 eyes (-28.25 D to +7.88 D spherical equivalent) of 128 patients (1-81 years) were examined by cycloplegic retinoscopy. All of them were measured with the PowerRefractor under cycloplegia. Fifty-four of these patients (108 eyes) were additionally measured without cycloplegia. The technique of the device is based on the eccentric photorefraction method. Both eyes can be measured simultaneously from a distance of 1 m. A video-analysis of each eye is computed in three meridians. The subject can be observed in real time on a screen, and the refraction is immediately available. Measurement of refraction was possible at all ages. More effort was required with young children who could not cooperate well with the procedure of conventional table-top autorefractometers. The mean sensitivity in detection of any amblyogenic ametropia was 80% with and without cycloplegia. The specificity was 61% with cycloplegia and 84% without. The rate of false-negative results in the detection of anisometropia, hyperopia and astigmatism ranged from 10% to 24%. In particular, high astigmatism and hyperopia remained undiscovered. The reliability of the photorefractor which was the subject of the evaluation in detecting amblyogenic ametropia was comparable to that of other devices described previously in the literature. The method is suitable for use in children, but anisometropia, high astigmatic and hyperopic ametropia remained undiscovered in several cases. Commercial interest: none.

Validade da citologia cervicovaginal na detecção de lesões pré-neoplásicas e neoplásicas de colo de útero

Introdução: O exame colpocitológico ou teste de Papanicolaou permite o diagnóstico precoce do câncer de colo do útero. O êxito no rastreamento desta doença dependerá, além de outros fatores, da acuidade diagnóstica do exame colpocitológico. Objetivos: Avaliar a acurácia diagnóstica da citologia cervicovaginal na detecção de lesões cervicais através da comparação citoistopatológica. Material e métodos: Avaliou-se o grau de concordância entre os exames citológico e histopatológico de 373 pacientes atendidas em um hospital universitário no período de 1990 a 1997 e foram calculados os indicadores: sensibilidade, especificidade, valores preditivos positivos e negativos e as taxas de falsos positivos e falsos negativos do exame. Resultados: A taxa bruta de concordância citoistopatológica foi de 65,1%. A sensibilidade do exame foi alta (96,0%), no entanto sua especificidade foi baixa (51,5%), significando a inclusão de muitos resultados falsos positivos. A taxa de falsos positivos foi de 48,4%, enquanto a de falsos negativos foi de 4%. Discussão: Apesar de a sensibilidade do teste ser alta, sua especificidade é baixa, significando que muitas mulheres seriam falsamente diagnosticadas como doentes, levando a um número elevado de resultados falsos positivos e custos desnecessários, além do potencial caráter iatrogênico que esta ação poderia assumir. No entanto, um exame altamente sensível é o teste de escolha para programas de rastreamento de câncer cervical na população feminina. Conclusões: Para garantir a acuidade diagnóstica do teste de Papanicolaou são essenciais atividades de controle de qualidade nos laboratórios, tanto do procedimento colpocitológico quanto do histopatológico, permitindo, assim, o êxito na detecção precoce e no tratamento das lesões cervicais.

Routine vs extensive malignancy search for adult dermatomyositis and polymyositis: a study of 40 patients.

To identify potential risk factors and the yield of routine screens for early detection of malignancy associated with dermatomyositis (DM) and polymyositis (PM). Retrospective study of malignancies in all patients with DM or PM followed up between the years 1981 and 2000 and a review of the relationship of DM and PM to malignancy, the usefulness of various tests or examinations for malignancy search, and the patients' course. Departments of internal medicine and dermatology in a teaching hospital. Forty consecutive adult patients with DM (33 cases) or PM (7 cases). (1) Rate of false-negative results of routine workup and yield (percentage of positive results) of blind malignancy search and (2) comparison of 16 characteristics in patients with malignancy vs those without. Malignancy occurred in 16 patients: 13 with DM and 3 with PM. In all cases, the diagnosis of malignancy was made concurrently with or shortly after the diagnosis of DM or PM. Factors associated with malignancy were recruitment in the internal medicine department (P =.02), constitutional symptoms (P<.01), a rapid onset of DM or PM (P =.02), the lack of Raynaud phenomenon (P<.01), and a higher mean erythrocyte sedimentation rate (P<.01) and creatine kinase level (P<.01). Initial routine search failed to discover 4 malignancies, 3 of which were discovered at an advanced stage by more extensive investigations. The positive result yield of blind malignancy search was only 13% (11 of 87), but reached 28% (5 of 18) for blind abdominal-pelvic and thoracic computed tomographic scans. Extensive search for malignancy, particularly computed tomographic scans, may be warranted in at least a subset of patients with DM or PM and risk factors of malignancy.

The reliability of diagnosis of infection during revision arthroplasties.

Follow up studies have shown that 0.5 to 4% of the total joint arthroplasties will be complicated by infection. Distinction between aseptic loosening and infection is important for prediction of the final outcome after revision arhtroplasty but also for the choice of operative treatment. However, diagnosis of low grade chronic infection is extremely demanding. 68 hip and knee revision arthroplasties were reviewed retrospectively in order to evaluate the reliability of pre- and perioperative analysis of infection during total joint revision arthroplasties. The sensitivity and specificity for clinical signs, blood white-cell count, C-reactive protein level, radiographic analysis, bone and leukocyte scans, joint aspirations, and gram staining were determined. Tissue sample were harvested and cultured in all cases. Positive cultures were regarded as a true infection. We were not able to characterize the infection by clinical signs. Also no single test was able to show the presence of infection in all cases. The best results were obtained from pre- and perioperative joint aspirations. Joint aspiration showed 1.0 specificity and 0.75 sensitivity. It is clear from this study that no single test is able to show the presence of infection in every case. Classical clinical signs, laboratory tests, special imaging studies and joint aspirations have all yielded a notable rate of false negative results. Therefore, we recommend that, if arthroplasty patients have pain in prosthetic joint without clear radiological evidence of loosening, bone scans and preoperative joint aspirations should be undertaken. Also, if radiological evidence of loosening is accompanied with one or more of following criteria; C-reactive protein level elevated, radiologic evidence of infection, loosening within the first five years after implantation. In case of infection a delayed two-stage reconstruction should be managed.

The value of temporary external lumbar CSF drainage in predicting the outcome of shunting on normal pressure hydrocephalus

Objective: It has been reported that temporary external lumbar CSF drainage (ELD) is a very accurate test for predicting the outcome after ventricular shunting in patients with normal pressure hydrocephalus...

Management of bloody nipple discharge.

Bloody nipple discharge causes a high degree of anxiety in women because of fear of breast cancer. Commonly, the absence of palpable or mammographic abnormalities gives a false sense of security, causing delays in diagnosis. Initial evaluation with physical examination and mammography is useful in detecting high-risk cases. Bloody nipple discharge is most frequently benign. It is caused by intraductal papilloma, duct ectasia, and less frequently by breast cancer. Several diagnostic tests have been proposed to establish the cause of bloody nipple discharge. Galactography, ultrasound, and exfoliative cytology are useful only when positive, but have a high rate of false-negative results and do not preclude histologic diagnosis. More recently, ductal lavages in combination with cytology have provided promising results, but experience and long-term follow-up are limited. Traditional treatment is surgical excision of the involved ductal system from which the discharge emanates. Ductal excision has been the only reliable procedure in establishing a certain diagnosis and in controlling the bloody discharge. The early success reported with image-guided excision of papilloma and duct endoscopy promises a significant improvement in our diagnostic accuracy from minimally invasive emerging technology.

Validation of a Polymerase Chain Reaction Method for the Detection of Rendered Bovine-Derived Materials in Feedstuffs

This study validated a polymerase chain reaction–based method for the detection of a specific bovine mitochondrial gene derived from rendered bovine tissues and admixed with complete animal feed. Four laboratories participated in this effort: one state laboratory and three Food and Drug Administration (FDA) laboratories, including one FDA field laboratory. The protocol used a statistical approach of 90% probability, with a 95% confidence interval for determining acceptable rates of false-positive and false-negative samples. Each participating laboratory analyzed 30 samples of feed each containing 0, 0.125, and 2.0% bovine meat and bone meal (BMBM), for a total of 90 feed samples. The samples were randomized such that the analysts were unaware of the true identity of the test samples. The results demonstrated that all laboratories met the acceptance criteria established for this protocol. The overall rates of false-negative results were 0.83% (1/120) at the level of 0.125% BMBM and 1.67% (2/120) at the level of 2% BMBM. The overall rate of false-negative results for all levels of BMBM was 1.25% (3/240). The rate for false-positive results was 0.83%.

Ultrasound examination of regional lymph nodes significantly improves early detection of locoregional metastases during the follow-up of patients with cutaneous melanoma: results of a prospective study of 1288 patients.

In regional lymph node metastasis of cutaneous melanoma, the number and volume of involved lymph nodes are the most important prognostic factors. Several studies have revealed that palpation of the lymphatic drainage area(s) and regional lymph nodes has a high rate of false-negative results during follow-up. The aim of the current study was to assess the sensitivity and specificity of ultrasound versus clinical diagnosis in the detection of subcutaneous and regional metastases. During a period of 42 months, a total of 6328 lymphatic drainage areas were examined clinically and by ultrasound (7.5-10 MHz) in 1288 melanoma patients at 4435 follow-up consultations. When an ultrasound finding was suggestive of metastasis, surgery and histopathologic evaluation were performed. The results of clinical examination, ultrasound examination, and histopathologic findings were compared. In 504 ultrasound examinations performed on 235 patients, metastatic disease was diagnosed in 263 examinations following surgery (179 patients). Due to advanced disease or rejection, an additional 56 patients did not undergo surgery. In 239 of the 263 positive findings (90.9%), metastases from melanoma were histopathologically confirmed. In 8 cases (3%) a second malignancy and in 16 cases (6. 1%) benign lymphadenopathy was histopathologically diagnosed. Palpation of subcutaneous lymph nodes and lymph nodes gave false-negative results in 68 of the 238 cases of histopathologically proven metastases (28.6%). Clinical examination was least sensitive in the supraclavicular, axillary, and infraclavicular regions. The sensitivity and specificity for ultrasound examination were 89.2% and 99.7%, respectively, and 71.4% and 99.7% for clinical examination, respectively. For early diagnosis of in-transit and regional lymph node metastases in cutaneous melanoma, ultrasound scanning is distinctly superior to clinical examination. Controlled follow-up studies are proposed to examine the possible beneficial effects on survival time resulting from the ultrasound examinations of the lymphatic drainage area(s) and regional lymph nodes.

4716 Prospective evaluation of the effect of blood on rapid urease testing.

BACKGROUND: RUT of H.Pylori (Hp) is especially important in patients who present with bleeding peptic ulcer since eradication of Hp is associated with a decreased rate of recurrent bleeding. RUT is associated with a variable false-negative rate that can be as high as 40 % in acute ulcer bleeding. The reason for this high false-negative rate is not known but the presence of blood has been one of the factors hypothesized to interfere with the results of RUT. AIM: this is a prospective evaluation of the effect of soaking gastric biopsy specimens in blood on the results of a commercially available RUT (HPfast), and the relationship of these results to blood group type. METHODS: Inclusion criteria : subjects undergoing EGD for standard clinical indications. Exclusion criteria: exposure to antibiotics, bismuth or proton pump inhibitors during the month prior to EGD. At the time of endoscopy, three biopsy specimens were taken from appearing normal antral mucosa. Before the biopsies were taken, 3 ml of blood was drawn from each patient. One specimen was sent for histology examination with H & E; a second specimen was submerged for 1 minute in 0.5 ml of blood that had been obtained immediately before from the same patient and was then placed on a HPfast slide. The third sample was directly placed on the HPfast slide but allowing a full minute to elapse, thus equaling the time the other specimen was submerged in blood. Given a prevalence of around 50 % of Hp infection in our hospital, demonstrating a lack of equivalence of 40 % from the baseline (0.5 x 0.4= 20 %) required 103 pairs of specimens (a0.05, power 0.8). Non-paired proportional data (results of blood-soaked vs. standard specimen RUT)were compared with Chi square and Fisher's exact tests. Likelihood ratios (LR)with 95 % confidence intervals (CI) were used to compare RUT vs. histology results. RESULTS: 103 patients were enrolled. 50 % of histology specimens were positive for Hp. There was no statistical difference in false negatives rates between blood-soaked and standard RUT specimens (27 % vs. 25 %). No difference was found between the LRs of a negative test for standard RUT (0.27, 95 % CI 0.17 to 0.43)and that of blood-soaked RUT specimens (0.28, 95 % CI 0.18 TO 0.43). When the results were analyzed according to blood type of the patients, no difference was found in the representation of ABO or RH systems. CONCLUSIONS: other factors must be sought to explain the high rate of false negative results of RUTs in the setting of acute ulcer bleeding since blood does not appear to interfere with the performance of these tests.

Clinical use of capillary PCR to diagnose Mycoplasma pneumonia.

In the present study, serologic data were compared with data obtained by capillary PCR to establish the efficacy of capillary PCR for the determination of Mycoplasma infection in samples obtained from throat swabs, bronchoalveolar lavage fluids (BALF), and sputum of patients with Mycoplasma pneumonia. We performed PCR analysis for Mycoplasma DNA on a total of 325 samples from 197 patients with community-acquired pneumonia and in whom Mycoplasma pneumonia was suspected. There were 68 PCR-positive specimens. Review of the differences in PCR positivity rates based on the site of specimen collection showed the highest rate of detection (28.6%) from throat swabs. From among the 31 patients with significantly elevated titers of serum Mycoplasma antibodies, the PCR results were positive for 25 patients. Thus, capillary PCR had a sensitivity of 80.6% (25 of 31). Five of the six false-negative results were from throat swab specimens. Moreover, testing (PCR) had been performed only once for these five patients with false-negative results. From among the PCR-positive findings from BALF specimens, there were no false-positive results. BALF specimens were very useful, except for the technical procedures and increased patient burden required to obtain these specimens. We suggest that the use of throat swab specimens in capillary PCR is much more suitable for diagnosing Mycoplasma pneumonia in routine clinical practice; however, careful throat swab specimen collection and an increase in the number of times that the PCR is performed are necessary to reduce the rate of false-negative results.

Review of criteria appropriate for a very low probability of pulmonary embolism on ventilation-perfusion lung scans: a position paper.

The "low-probability" interpretation of ventilation-perfusion lung scans has been characterized as misleading or even dangerous because of the high prevalence of pulmonary embolism associated with such an interpretation. Since the completion of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study, analyses of the PIOPED database have allowed identification of several abnormalities seen on ventilation-perfusion scans that have a positive predictive value (PPV) for pulmonary embolism of less than 10%. These include nonsegmental perfusion abnormalities (PPV = 8%), perfusion defects smaller than the corresponding areas of increased opacity at chest radiography (PPV = 8%), matched ventilation-perfusion abnormalities in two or three zones of a single lung (PPV = 3%), one to three small segmental perfusion defects (PPV = 1%), triple matched defects in the upper or middle lung zone (PPV = 4%), and the stripe sign (PPV = 7%). Use of these abnormalities as interpretative criteria constitutes "very low probability" interpretation and will reduce the number of low-probability interpretations of ventilation-perfusion lung scans, which may be considered nondiagnostic because of the unacceptably high rate of false-negative results. This will enhance the utility of the ventilation-perfusion lung scan for screening patients with suspected pulmonary embolism.