Addressing the problem of hook effect in sandwich lateral flow immunoassay: review and impact on future solutions / 中华检验医学杂志

Lateral flow immunoassay (LFIA) is a rapid detection technique that allows researchers to move the antigen-antibody reaction from a test tube or laboratory vessel to a test strip. Due to the chromatographic effect of the test strip, the solution would move to a specified direction based on the test and complete the whole antigen-antibody specific reaction. A qualitative judgment can be made with the naked eye by observing the color change of the reagent strip at a specific location. Because of its advantages of being fast, simple, specific, inexpensive, and requiring no specialized personnel, LFIA is now widely used in medical testing, food quality monitoring, environmental monitoring, agriculture and animal husbandry. A major bottleneck for the development of LFIA technology is the hook effect. This paper summarizes the current methods, means and research progresses to combat the hook effect, hoping to provide a strong technical reference for researchers to design test strips, select suitable nanoparticles, and achieve quantitative LFIA detection.

Application value of modified magnetic bead screening for enrichment of cell-free fetal DNA from maternal peripheral blood in non-invasive prenatal testing / 中华围产医学杂志

Objective:To evaluate the value of modified magnetic bead screening for enrichment of cell-free fetal DNA (cffDNA) in non-invasive prenatal testing (NIPT).Methods:This study retrospectively recruited 31 cases with low concentration of cffDNA (<6.00%), Z value in the gray zone (3.00-4.00) at the first detection, or false-positive (confirmed by invasive prenatal diagnosis) or false-negative (confirmed by postnatal chromosome test) results among 11 000 pregnant women who underwent routine NIPT in Beijing Haidian District Maternal and Child Health Care Hospital from October 2017 to December 2019. Plasma samples collected for the first-time routine NIPT were used to enrich cffDNA using modified magnetic beads for NIPT (modified NIPT). Wilcoxon rank sum test was used to compare the modified NIPT with the routine NIPT in detecting the cffDNA concentrations of male fetuses.Results:Among the 31 pregnant women, there were 13 cases with low cffDNA concentration in routine NIPT, 11 having false-positive results in the routine NIPT (three for trisomy 13, four for trisomy 18 and four for trisomy 21, all were confirmed by invasive prenatal diagnosis), six with gray-zone Z values in the first-time NIPT (retesting indicating low risk) and one having false negative result for trisomy 21 (confirmed by postnatal chromosome test). Cell-free DNA (cfDNA) fragments less than 150 bp were effectively enriched using the modified magnetic bead screening and the concentration of cffDNA was increased from 4.43% (2.45%-17.61%) in routine NIPT to 13.46% (7.75%-36.64%) in the modified NIPT ( Z=-14.22, P<0.01). Results of the modified NIPT indicated that 13 cases with low cffDNA concentration of routine NIPT were successfully detected as low risk, as well as the risks in the six cases with gray-zone Z value and six of the 11 false-positive cases in the routine NIPT were low, which were consistent with the retest results of the routine NIPT, while high risk was found in one false-negative case. Conclusions:The modified NIPT could reduce the false positive rate by lowering the failure rate caused by low concentration of cffDNA and is able to identify false-negative cases. Compared with the routine NIPT, it shows a higher success rate and a lower false positive rate.

HIV nucleic acid results and follow-up of 73 WB negative and indeterminate samples in Dujiangyan area / 中华检验医学杂志

Objective:To test the HIV virus nucleic acid using immunoblot method (Western blotting, WB) and to follow-up with the negative and indeterminate samples in the Dujiangyan area, compare the WB and nucleic acid results before and after followed-up, and try to reduce the WB band′s false-negatives and false-positives.Methods:The 286 suspected HIV infection samples in the Dujiangyan region from January to October 2021 were confirmed by WB, the HIV virus load were tested for the samples that were WB negative and WB indeterminate, those patients were followed-up with epidemiological history and viral load results, and the results before and after tracking were compared.Results:In the 286 samples of suspected HIV infection included in this study, we reported 213 (74.48%) WB positive, 37 WB negative (12.94%), and 36 WB indeterminate (12.58%); 10 of 37 WB negative samples were followed-up; 18 of 36 WB indeterminate samples were followed-up. Among the followed-up WB negative and indeterminate samples, 17 of them had virus nucleic acid detection prior to the follow-up, and all of them turned positive after following-up. The others with no previous virus nucleic acid detection were confirmed to be negative.Conclusions:Among the followed-up samples, 2 samples were false-negative in WB negative results, and 3 were false-positive in WB indeterminate results. The viral nucleic acid must be tested and followed-up in WB negative and indeterminate samples.

Dificultades en la detección de genomas del nuevo coronavirus 2 (SARS CoV-2) / Pandemic and social inequiality: the popular neighborhoods of the Buenos Aires suburbs in preventive social isolation

RESUMEN El manejo de las infecciones virales respiratorias, tanto a nivel nacional como a nivel mundial, requiere resultados científicos de calidad. La reacción en cadena de la polimerasa de transcriptasa inversa (rRT-PCR, por su sigla en inglés) es considerada el "patrón de oro" para detectar el genoma del nuevo coronavirus 2 (SARS-CoV-2), agente causal de la enfermedad por el nuevo coronavirus (COVID-19) sobre todo en la fase aguda de la infección. Su uso es controvertido fuera de un contexto de exposición viral. El objetivo del presente trabajo es analizar escollos encontrados durante la detección del genoma del SARS-CoV-2 que pueden producir resultados falsos. Los falsos negativos de rRT-PCR pueden deberse al momento y la eficacia de la toma de la muestra, la congelación, el almacenamiento y la descongelación, y a la inactivación térmica de la virulencia. Además, las señales retardadas de los controles internos invalidan la negatividad. Por otra parte, las muestras con escaso material biológico llevan a conclusiones negativas falsas, por lo que determinar un umbral (número mínimo de células epiteliales) contribuirá a reducirlas. Sin embargo, la mayoría de los kits detectan ADN humano, pero no fueron calibrados para cuantificar carga celular. Los ácidos ribonucleicos nucleares (ARN) virales adheridos a guantes, tubos y gorros, -entre otros elementos-, son fuente de falsos positivos. Las farmacopeas sugieren que la contaminación externa se controle en series de 100 muestras con al menos una representatividad del 10%. Si se extrapola esta aproximación al laboratorio de análisis clínicos, en lugar de uno se deberían procesar al menos 10 controles negativos contiguos a 10 positivos cada 100 pruebas. Mejorar la detección por rRT-PCR implica un aumento de al menos 20% en el costo de los reactivos, por lo que se necesitan recursos adicionales.

ABSTRACT Emerging respiratory viral infections like the severe coronavirus disease (CoVID 19) caused by novel coronavirus 2 (SARS-CoV-2) require quality results for science-based responses. The reverse transcriptase polymerase chain reaction (rRT-PCR) is considered the gold standard for detecting SARS-CoV-2 (particularly in the acute phase of infection). The aim of the present work was to analyze pitfalls during the search of viral genomes. False negative conclusions are result of sampling timing, performances of swabbing, storage, and thawing and heat-infectivity inactivation. Samples with low biologic material also lead to false negatives. Qualitative controls to detect the presence of human DNA are available in several kits but they were not calibrated for quantification of human cell loads. Moreover, negativity cannot be reported for samples with delayed signals for the internal control (due to deficiency in extraction and/or retro transcription and/or or to the presence of rRT-PCR inhibitors). The viral RNA that may have stick on gloves, on tubes, caps, etc. may produce false positives. The International Pharmacopoeias recommend for external contamination to test at least 10% of the samples. Couples of 10 negative contiguous to 10 positive controls randomly distributed should be therefore included in each series of 100 rRT-PCR tests. These improvements increase the cost of each determination (at least by 20% only for the reactants) and require additional resources.

Analysis of false negative results in throat swab nucleic acid test of severe acute resporatory syndrome coronavirus 2 / 第二军医大学学报

Objective To investigate the false negative rate of throat swab nucleic acid test of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to analyze the causes, so as to provide references for the prevention and control of coronavirus disease 2019 (COVID-19) in China. Methods A retrospective analysis was conducted on the throat swab nucleic acid test results of 1 452 COVID-19 patients admitted to Guanggu Branch of Maternity and Child Healthcare Hospital of Hubei Province from Feb. 19 to Mar. 20, 2020. The negative results before positive results at discharge were judged as false negative results, and the false negative rate was calculated. The discharged patients were followed up to screen for the patients who were positive for nucleic acid test again, and the relationship between the times of consecutive negative nucleic acid tests before discharge and the positive again results was analyzed. Results Among the 1 452 COVID-19 patients, 592 (40.77%) were males and 860 (59.23%) were females. A total of 212 cases (14.60%) had false negative results. Twenty-eight cases (1.93%) were discovered nucleic acid positive again after discharge. Among the 918 patients whose nucleic acid tests were negative for two consecutive times, 24 (2.61%) were positive again, which was significantly higher than that of the patients whose nucleic acid tests were negative for three consecutive times (0.75%, 4/534; χ2=6.21, P=0.012 7). Conclusion The throat swab nucleic acid test of SARS-CoV-2 has a certain proportion of false negative results, which is one of the reasons for COVID-19 patients are found nucleic acid positive again after discharge. Multiple and continuous tests by different testers are recommended before discharge, and negative nucleic acid test for three or more consecutive times can reduce the incidence of nucleic acid positive results again after discharge.

Analysis of false-negative results for 2019 novel coronavirus nucleic acid test and related countermeasures / 中华检验医学杂志

In December 2019, a cluster of patients with pneumonia of unknown cause were linked to a seafood wholesale market in Wuhan, China. Some studies found that the virus was a new kind of virus which had never been found in the human body. Then, the virus was named 2019 Novel Coronavirus (2019-nCoV) by the World Health Organization (WHO). 2019-nCoV nucleic acid detection is one of the essential indicators of NCP (Novel Coronavirus Pneumonia). Recently, some false-negative cases in China-Japan Friendship Hospital and Hangzhou Hospital led the clinical doctors to question the value of the nucleic acid detection. In this paper, more than 3 000 results of 2019-nCoV detection in Zhongnan Hospital, Wuhan University were analyzed. Attention should be paid to the root cause of false-negative results and the related countermeasures should be taken.

False negative non-invasive prenatal screening result for trisomy 18: a case report / 中华围产医学杂志

We hereby reported a case of false negative non-invasive prenatal screening (NIPS) for trisomy 18. The fetus with increased nuchal translucency (3.2 mm) detected by ultrasound scan at 13+4 gestational weeks received NIPS and the result was negative in chromosomes 21, 18 and 13. A routine ultrasound examination at 22 weeks of gestation revealed multiple anomalies and a second NIPS was offered, which showed a negative result again. The pregnancy was terminated at 22+3 weeks. Multiple fetal and placental biopsies were collected for chromosome analysis using copy number variation sequencing based on high-throughput sequencing and fluorescence in situ hybridization. The fetal karyotype was shown to be 47,XY,+18 in fetal tissues (skin and liver) and umbilical cord, while no chromosomal abnormalities was detected at or near the center of the fetal and maternal surface of the placenta. Results of the chromosomal analysis along the edges of the fetal and maternal surfaces of the placenta were Chr18:47,XY,+18[60]/46,XY[40] and Chr18:47,XY,+18[35]/46,XY[65], respectively. We inferred that placental mosaicism was the cause of the false negative NIPS result. Therefore, genetic counseling before and after NIPS is necessary. Follow-up ultrasound is important for NIPS-negative patients. Invasive prenatal diagnosis is recommended when abnormal ultrasound markers with possible genetic etiology were recognized.

Is the frozen section examination for sentinel lymph node necessary in early breast cancer patients?

PURPOSE: Sentinel lymph node (SLN) biopsy (SLNB) is widely performed for axillary staging in patients with breast cancer. Based on the results of frozen section examination (FSE), surgeons can decide to continue further axillary dissections. This study aimed to verify the accuracy of FSE for SLNs. METHODS: We reviewed the records of 4,219 patients who underwent SLNB for primary invasive breast cancer between 2007 and 2016 at the Severance Hospital. We evaluated factors associated with the false-negative results of FSE for SLNs using the Generalized Estimating Equations model. RESULTS: A total of 1,397 SLNs from 908 patients were confirmed to be metastatic. Seventy-one patients (1.7%) had confirmed pathologic N2 or N3 stage. Among metastatic SLNs, micrometastasis was found in 234 (16.8%). The overall accuracy of SLNB was 98.5%. The sensitivity and false-negative rate of FSE were 86.4% and 13.6%, respectively. Several clinicopathological factors, including the size of SLN metastases, suspicious preoperative axillary lymph nodes, and luminal B subtype, were associated with a higher rate of false-negative results. CONCLUSION: Most patients were not indicated for axillary lymph node dissection. Some patients may show transition in their permanent pathology due to the size of the metastatic node. However, the false-negative results of FSE for SLNs based on the size of the metastatic node did not change our practice. Therefore, intraoperative FSE for SLN should not be routinely performed for all breast cancer patients.

False-negative reactions to the comparative intradermal tuberculin test for bovine tuberculosis / Reações falso-negativas ao teste cervical comparativo para tuberculose bovina

According to the Brazilian National Program for the Control and Eradication of Animal Brucellosis and Tuberculosis (PNCEBT), the routine tests for the diagnosis of bovine tuberculosis in the country are the simple intradermal tuberculin test (SITT) of the Ministry of Agriculture, Livestock and Food Supply (MAPA), the caudal fold test and the comparative intradermal tuberculin test (CITT). The latter is also used as a confirmatory test. A group of 53 animals from three dairy herds in a focal area for bovine tuberculosis, that were submitted to depopulation in the state of Rio Grande do Sul, were submitted to the CITT. Tissues were cultured and the resulting colonies were confirmed by PCR and DNA sequencing. Among the 53 animals analyzed using the CITT, 32 (60.4%) were negative, 14 (26.4%) were positive and seven (13.2%) results were inconclusive. The CITT detected 11 of the 39 animals with culture-confirmed M. bovis infection as positive. Among the total of 14 uninfected animals based on cultures, the CBT detected eight as negative. Thus, the CITT demonstrated sensitivity of 28.2% and specificity of 57.1% for the population sampled. A total of 24/32 (75.0%) of the animals with negative CITT results were culture positive (confirmed by PCR) and were considered false negatives based on the CITT. The maintenance of these false-negative animals in herds has serious implications for the control of the disease, since they can be a source of infection. The addition of complementary tests could help identify such animals and increase the odds of diagnostic success.(AU)

No Brasil, segundo o Programa Nacional de Controle e Erradicação da Brucelose e Tuberculose Animal (PNCEBT), do Ministério da Agricultura, Pecuária e Abastecimento (MAPA), os testes de rotina para o diagnóstico de tuberculose bovina são o teste cervical simples (TCC), o teste da prega caudal (TPC) e o teste cervical comparativo (TCC), sendo que o último também é utilizado como teste confirmatório. Um grupo de 53 animais oriundos de três rebanhos leiteiros de área de foco para tuberculose bovina que foram submetidos a vazio sanitário no Rio Grande do Sul foi submetido ao TCC. Os tecidos destes animais foram cultivados e as colônias resultantes confirmadas por PCR e sequenciamento de DNA. Dos 53 animais analisados no TCC, 32 (60,4%) foram negativos, 14 (26,4%) positivos e sete (13,2%) inconclusivos, com base no PNCEBT. O TCC detectou como positivos 11 dos 39 animais com infecção por M. bovis confirmada por cultivo. Do total de 14 animais não infectados, baseado na cultura, o TCC detectou oito como negativos. Assim, o TCC apresentou, para a população amostrada, sensibilidade de 28,2% e especificidade de 57,1%. Um total de 24/32 (75,0%) dos animais negativos ao TCC foi positivo no cultivo (confirmado por PCR), sendo considerados falso-negativos ao TCC. A manutenção destes animais falso-negativos nos rebanhos tem sérias implicações para o controle da enfermidade, já que os mesmos podem ser fonte de infecção. A adição de testes complementares poderia auxiliar na identificação destes animais, aumentando a cobertura diagnóstica.(AU)

Influence of visual field results in the glaucoma diagnosis / Influência dos resultados do campo visual no diagnóstico de glaucoma

Abstract Objective: To determine the influence of visual field results in the diagnosis of glaucoma. Methods: A questionnaire with ophthalmologists was conducted where slides of a digital photograph of the optic disc and computerized visual field exam were presented.(Physicians were instructed to answer whether glaucoma was observed in each of the slides). No other information was given to those examiners. Half of the patients had glaucoma with corresponding visual field, and the other half had physiological cupping and normal visual field. The slides were equally divided between retinography and corresponding visual field (same patient) and exams randomly exchanged, where an optic disc of glaucoma with a normal visual field was placed, and vice-versa. The order in which the slides were presented was also randomized. Results: Forty slides were evaluated by 29 ophthalmologists. No glaucoma specialist was included. The overall agreement among the examiners (Kappa) was 0.270 ± 0.281, and 0.261 ± 0.238 for the exams of the same eye and was 0.274 ± 0.217 from the slides with the exams changed (p=0.4). The diagnosis was made correctly in glaucoma patients with corresponding visual field exam in 66.89% of the cases, and in 66.20% of patients with physiological cupping. When the exams were exchanged, the results dropped to 34.13% and 35.86%, respectively (p<0.001 for both). Conclusion: Visual field results may influence the diagnosis of glaucoma by non-glaucoma specialists.

Resumo Objetivo: Avaliar a influência da campimetria computadorizada no diagnóstico do glaucoma. Métodos: Foi realizado questionário com oftalmologistas apresentando slides com uma fotografia digital de disco óptico e campo visual computadorizado. Os médicos deveriam assinalar se o exames apresentados eram de glaucoma ou não. Nenhuma outra informação foi passada para os examinadores. Metade dos pacientes apresentavam glaucoma com dano correspondente de campo visual, e a outra metade aumento fisiológico da escavação e campo visual normal. Os slides foram igualmente divididos em: retinografia e campo visual correspondentes (mesmo paciente) e exames invertidos de forma aleatória, colocando um disco óptico de glaucoma com um campo visual normal e vice-versa. A ordem de apresentação dos slides foi randomizada previamente. Resultados: Foram incluídos 40 slides, avaliados por 29 oftalmologistas. Nenhum especialista em glaucoma foi incluído. A concordância entre os examinadores (Kappa) foi de 0,270 ± 0,281, sendo de 0,261 ± 0,238 para os exames correspondentes e 0,274 ± 0,217 para os slides com os exames trocados (p=0,4). O diagnóstico foi realizado corretamente nos pacientes com glaucoma com o campo visual correspondente em 66,89% dos casos, e em 66,20% nos pacientes com aumento da escavação (normais). Quando houve a troca da correspondência dos exames, os valores caíram para 34,13% e 35,86%, respectivamente (p<0,001 para ambos). Conclusão: O conhecimento prévio dos resultados do campo visual pode influenciar o diagnóstico do glaucoma.

False-negative Possibility in Genetic Test of Congenital Long QT Syndrome by Next-generation Sequencing / 中国循环杂志

Objective: To explore the false-negative possibility in genetic test of congenital long QT syndrome (LQTS) by next-generation sequencing (NGS). Methods: A total of 28 genomic DNA samples were collected from 4 laboratories including 2 commercial medical laboratories using HiSeq2000 platform as Lab1,n=6 and Lab2,n=8; 1 commercial research service laboratory using Ion-torrent platform as Lab3,n=8 and 1 academic laboratory using HiSeq2000 platform as Lab 4,n=6. Sequencing coverage in the exons of protein-coding region in 3 main LQTS pathogenic genes as KCNQ1, KCNH2, SCN5A and possible pathogenic variants were quantitatively analyzed. Results: In Lab1, Lab 2 and Lab 4 with HiSeq2000 platform, above 98% protein coding regions in 3 pathogenic genes were covered with>10-fold reads and 90%-95% were covered with>30-fold reads. In 2 commercial medical laboratories, 3.63% and 9.84% protein coding regions of KCNQ1 gene in 14 samples were covered with<10-fold reads and with<30-fold reads; lower than 10-fold covering region was focused in the 1st exon including about 2% known or likely pathogenic variants. In 2 commercial medical laboratories, 2.64% and 15.76% protein coding regions of KCNH2 gene in 14 samples were covered with<10-fold reads and with<30-fold reads; low covering region was located in multiple exons. For the data from Lab 1, as high as 28.56% protein coding regions of KCNH2 gene were covered with<30-fold reads including 113 (19.79%) known or likely pathogenic variants. SCN5A gene had the best coverage of protein coding region, with no<10-fold reads in all 4 Labs and no<30-fold reads in 2 commercial medical laboratories. Conclusion: Currently, NGS has low coverage region in both KCNQ1 and KCNH2 genes, pathogenic variants could be missed and false-negative possibility should be highly alert.

Diagnostic Accuracy for Malignancy in Open Surgical Biopsy of Neck Lymph Nodes / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The open surgical biopsy (OSB) of neck lymph nodes is considered a definite diagnostic procedure; however, the diagnostic accuracy of this procedure has not been fully studied. Thus, we aimed to identify the false negative rates of OSB for malignancy and the possible causes of misdiagnosis that might severely affect patient prognosis. SUBJECTS AND METHOD: We extracted the data from 495 OSB of neck lymph nodes between 2005 and 2012. The diagnostic accuracy of OSB of neck lymph nodes was estimated based on re-biopsy. In addition, we reviewed possible clinical factors related to false negativity, cause of misdiagnosis and its clinical impacts. RESULTS: The false negative rate of OSB of neck nodes was 2.2% with a risk of 3.8% false diagnosis among subjects with initial 'benign' results. The cases of the initial misdiagnosis (n=7) had the dismal outcomes (4 deaths, 1 disease progression). The main cause of misdiagnosis was the failure to target the disease-affected lymph nodes (85.7%). Malignancy-related symptoms persisted in all cases of misdiagnosis, which required re-biopsy. CONCLUSION: Accurate targeting of lymph nodes, close monitoring of clinical symptoms and comparison of biopsy results with symptoms are very important to reduce false negativity for malignancy in OSB of neck lymph nodes.

Clinical research of sentinel lymph node biopsy in patients with early breast cancers / 重庆医学

Objective To perform the sentinel lymph node biopsy (SLNB) in the patients with early breast cancer by the strict screening conditions and to analyze the accuracy of the sentinel lymph node for predicting the axillary lymph node status .Methods SLNB combined with methylene blue dye and isotope was performed in 266 cases of early breast cancer treated in this department with full treatment courses .Then the axillary lymph node dissection(ALND) was routinely conducted .With the pathological ex-amination as the standard ,the related factors affecting SLNB were analyzed .Results The detection rate of SLN ,accuracy rate ,sen-sitivity and the false negative rate were 100% ,98 .5% ,95 .56% and 4 .44% respectively ;the accuracy of SLN was significantly cor-related with the tumor size ,pathological type and axillary lymph node status(P<0 .01);the false negative rate of SLN was related with the tumor location(P<0 .05) .Conclusion The combination of methylene blue dye and isotope used in SLNB is feasible in the patients with early breast cancer ,SLN could accurately predict the axillary lymph node metastasis status .

The reasons of false-negative results in urine analysis and its improvement measures / 中国基层医药

Objective To explore the reasons of false-negative results in urine analysis and improvement measures.Methods Fresh morning urine specimen of 1 080 cases from January 2012 to March 2012 in our hospital were selected,and they were determined by dry chemical and sediment microscopic examination,then the results were compared between the two methods.Results 713 cases of white blood cells and 748 cases of red blood cells showed negative results by dry chemical method,while 692 cases of white blood cells and 723 cases of red blood cells showed negative results by sediment microscopic examination;The false negative rate of red blood cells and white blood cells by two methods were 2.95％,3.34％,the test results of the two methods showed no significant differences(x2 =0.900,1.330,all P ＞ 0.05).Conclusion The urine analysis should combine with dry chemical method and artificial microscopic urine analysis to improve the precision and accuracy of the test results,and to oliminate interference factors for avoiding undetected false detection.

Preliminary Evaluation of the URiSCAN SUPER and Usefulness of a New Urine Reagent Strip to Detect Ascorbic Acid / 임상검사와정도관리

BACKGROUND: Ascorbic acid can cause false negative results in the detection of urinary hemoglobin (Hb) with reagent test strips. The fully automated urine analyzer URiSCAN SUPER (YD Diagnostics, Korea), which can measure ascorbic acid, was recently developed. We compared the URiSCAN SUPER to the semi-automated urine analyzer URiSCAN PRO II (YD Diagnostics) and evaluated the usefulness of a new reagent strip to detect ascorbic acid. METHODS: A total of 641 urine samples were used to evaluate the agreement between the two analyzers. In addition we performed urine microscopic examinations to investigate the sensitivity and specificity of urinary Hb and white blood cells. We determined the detection limit of urine ascorbic acid. We also determined the positive rate of ascorbic acid and the false negative rate for urinary Hb. Additionally, the interference effect of ascorbic acid for urinary Hb was investigated. RESULTS: The agreement rate between the two analyzers was greater than 98% for all tests except for urinary specific gravity. The detection limit of urine ascorbic acid was 10 mg/dL. The positive rate of ascorbic acid was 49.8%. The false-negative rate for urinary Hb was 6.0% and 2.8% (P>0.05) in the presence and absence of urine ascorbic acid, respectively. CONCLUSIONS: The performances of the two urine analyzers were comparable. URiSCAN SUPER for the detection of urinary Hb was resistant to interference by ascorbic acid. Since the URiSCAN SUPER performs a fully automated analysis, it would be useful in urine screening.

False negative bone scan finding of vertebral metastatic compression fracture: A case report

Bone scan using (99m)Tc-MDP is the most accurate and reliable method for the early detection of fracture, and that is the screening procedure of choice for the demonstration of bone metastases. It is well known that it has superior sensitivity to radiography for this purpose. We report the case of 41 years old man with known primary tumor and metastatic vertebral fracture presenting false negative bone scan finding.

How to reduce the false negative rate of sentinel lymph node biopsy on breast cancer / 肿瘤

Objective: To investigate the reasons for false negative test results of sentinel lymph node (SLN) biopsy using isotope for patients with breast cancer and discuss how to reduce the false negative rate. Methods: The SLNs were identified in 150 breast cancer patients between May 2000 and May 2007. 99mTc-labeled dextran (99mTc-DX) was injected pre-operatively, then the localization of SLN was identified by γ-detecting probe intraoperatively, finally the removed SLNs were confirmed by routine pathological examination. Results: The detection rate of SLN biopsy was 96%. The sensitivity, specificity, false negative rate, false positive rate, and accuracy of SLN detection were 93.4%, 100%, 6.6%, 0%, and 97.2%, respectively. The positive and negative predictive value were 100% and 95.4%, respectively. Youden's index was 0.934. The false negative rate was associated with the selection of indication, anatomic variation, preoperative biopsy and radiotherapy, appearance of internal mammary SLN, multifocality, incomplete pathological examination and inexperienced skills. Conclusion: The false negative rate could be reduced to an acceptable degree gradually by strictly selecting indications for SLN biopsy, probing SLN location according to standard operating procedure, keeping seriousness, performing post-operative pathological examination.

Un problema de diagnóstico perinatal: pacientes serológicamente negativos pero infectados por el VIH / A perinatal diagnostic problem: HIV infected patients who are serologically negative

A 142 pacientes se les realizó ELISA, Inmuno blot de IgG, Inmuno blot de IgA (en los menores de 24 meses), determinación de antígeno en plasma, aislamiento viral por cultivo de detección de genoma viral por amplificación con la reacción de polimerasa en cadena (PCR). El diagnóstico integral demostró que 10 por ciento (14 pacientes) que resultaron negativos o indeterminados para detección de anticuerpos IgG anti-VIH-1, estaban infectados por el virus. Once de estos pacientes tienen entre 2 y 24 meses de edad; dos, entre 4 y 6.5 años, y uno, 30 años. El diagnóstico se emitió en cuatro de los casos por presencia de antígeno en plasma; en cinco por amplificación por PCR de ADN proviral presente en células mononucleares periféricas; en cuatro casos por PCR positivo e inmunofluorescencia (IF) del cultivo, y el último caso, presentó Inmuno blot positivo e IF del cultivo. Dichos casos presentan el problema de resultados falsos negativos por serología de anticuerpos anti-VIH, especialmente en niños menores de 24 meses

Comprehensive HIV diagnosis of 142 patients was done by ELISA, IgG immunoblot, IgA immunoblot (in patients under 24 months), plasma antigen determination, viral isolation by culture and genome detection by polymerasa chain reaction (PCR) amplification. Results showed that 14 patients (10%) with negative or indefinite results for anti-HIV-1 IgG antibody were in fact infected by the virus. Eleven of these patients were between 2 and 24 months of age, two between 4 and 6.5 years and one was 30 years old. Diagnosis was obtained by antigen positivity in four of them; by PCR amplification of peripheral mononuclear cells of proviral DNA in five of them; by PCR and immunofluorescence (II) of cultured cells in four cases, and the last diagnosis was made by IgG immunoblot and IF of the viral culture. These cases pose a problem because of false negative HIV serology, particularly in patients under 24 months of age.