[Pre- and post-operative sequential changes of serum p53 antibodies and clinical significance in patients with lung cancer]

BACKGROUND

To explore the relationship between serum p53 antibodies and clinicopathological characteristics in patients with lung cancer and to investigate sequential changing regularity of serump53 antibodies after surgical resection.

METHODS

The serum p53 antibody level was detected in 120 patients with lung cancer , and in 30 patients with benign pulmonary lesion and 120 healthy adults as control by enzyme linked immunosorbent assay ( ELISA) . The blood samples were collected on the day before operation and on the 7th , 30th and 90th days postoperatively.

RESULTS

The level and positive rate of serum p53 antibodies in patients with lung cancer were significantly higher than those in patients with benign pulmonary disease and normal individuals ( P < 0. 05) , but there was no significant difference between patients with benign pulmonary disease and normal individuals ( P > 0. 05) . The level and positive rate of pre-operative serum p53 antibodies in patients with lung cancer were closely related to cell differentiation and stage of lung cancer ( P < 0. 01 or P < 0. 05) . The level of serum p53 antibodies decreased gradually in patients with lung cancer underwent radical removal of the cancer , and completely returned to the normal level around the 30th day after operation , but the level of serum p53 antibodies in patients with lung cancer underwent palliative operation didn't reduce to the normal level on the 30th day after operation. It would increase again when tumor metastasis or recurrence developed.

CONCLUSIONS

Detection of serum p53 antibodies is helpful to defferentiate benign from malignant pulmonary diseases. Monitoring of sequential change of pre- and post-operative serum p53 antibodies in patients with lung cancer is helpful to evaluate response to treatment , to judge prognosis and to guide the comprehensive treatment of patients with lung cancer after operation.

[Tracheal carina reconstruction and bronchoplasty in the treatment of 94 central type bronchogenic carcinomas]

BACKGROUND

To analyze the short-term effects and long term survival of patients with lung cancer underwent tracheal carina reconstruction and bronchoplasty.

METHODS

From April 1985 to May 1999, 94 patients with lung cancer underwent tracheal carina reconstruction and bronchoplasty, 14 for carinal resection and reconstruction and 80 for bronchial sleeves.

RESULTS

Postoperative complications were atelectasis ( 19 cases) , arrthymia ( 2 cases) and anastomotic leakage ( 1 case) . There was no operative death in this series. The 1-, 3- and 5-year survival rates were 83. 1%( 74/ 89) , 58. 3%( 35/ 56) and 34. 0%( 18/ 53) respectively for the entire group. The 5-year survival rate was 66. 7%( 6/ 9) in stage Ñ B disease, 40%( 6/ 15) in Ò B disease and 21. 1%( 4/ 19) in Ó A disease. The indication of these procedures and the methods of lymph node dissection, bronchoplasty and pulmonary artery reconstruction, and superior vena cava reconstruction have been discussed.

CONCLUSIONS

Bronchoplasty for lung cancer is a safe and effective therapy. The long term survival depends on the stage of lung cancer , proper selection of surgical indication, clearance of lymph nodes in operation and multiple modality therpay after operation.

Temperature sensitivity of passive holographic wavelength-division multiplexers-demultiplexers

We derive a set of concise formulas to characterize the temperature sensitivity of holographic wavelength-division multiplexers-demultiplexers (H-MUX's-H-DMUX's). The normalized parameters such as dispersion abilities, central wavelength shift rate, and variations of insertion loss hold for general grating-based wavelength-division multiplexing-demultiplexing (WDM-WDDM) structures. The results are applicable to both wide-WDM-WDDM and dense ones working in 800-, 1300-, and 1550-nm optical wavelength windows, regardless of whether their input-output ports are single-mode or multimode fibers. Detailed analysis and experiments are carried out on a fully packaged four-channel H-MUX-H-DMUX. The experimental results at temperatures from 25 to 80 degrees C fit nicely with the theoretical prediction. We conclude that passive grating-based H-MUX's-H-DMUX's are promising for meeting the requirements on temperature sensitivity in optical data communications and telecommunications. Most of the analysis can be applied to other types of Bragg-grating-based WDM-WDDM.

[Effects of ultrasonography on evaluating the status of cervical lymphatic metastasis in patients with oral squamous cell carcinoma]

OBJECTIVE

To investigate effects of ultrasonography on evaluating the status of cervical lymphatic metastasis in patients with oral squamous cell carcinoma (OSCC).

METHODS

Nineteen OSCC patients with the diagnosis confirmed by biopsy of primary focus were included in this study. All the patients were hospitalized in the department of stomatology, Beijing Medical University during June, 1995 and June, 1996, among them there were 13 men and 6 women. The ages were ranged from 31 to 71 years old, with the average of 54.4 years old. The primary focus of 13 cases were in tongue, 3 cases in cheek, 2 cases in gum, and 1 case in the conjunction of gum, mouth floor and tongue respectively. All the patients were examined by ultrasonography prior to operation, and operated with the procedures of excision of primary focus and radical neck dissection. The length, width, Vmax and Vmin and Resistance Index (RI = (Vmax-Vmin)/Vmax) of blood flow of cervical lymphatic nodes were measured with acuson 128 xp/10 color Doppler flow imaging scanner with a 7.5 MHz probe. The total of 34 cervical lymphatic nodes were examined by the scanner. L/W ratios in all nodes, RI and Vmax in 16 nodes were obtained respectively. All results were divided into two groups, metastases and non-metastases groups based on the pathological findings for further statistic analysis. Student t test was employed in the study.

RESULTS

The average L/W ratios, the average Vmax and the average RI were 1.95 and 2.17, 0.24 and 0.14, and 0.80 and 0.56 in metastases and non-metastases groups respectively. There was a significant difference between RI in two groups, but no statistical differences were revealed in L/W ratios and Vmax, despite the great difference in the average Vmax in the two groups. When RI > or = 0.65 and Vmax > or = 0.20 m/s were regarded as the criterion for positive diagnosis, the accuracy rate, the sensibility and the specificity was 91.2%, 90%, and 91.7% respectively in making diagnosis of OSCC.

CONCLUSION

The status of cervical lymphatic metastases in OSCC patients could be evaluated accurately by the color Doppler flow imaging scanner, which might be helpful in making accurately diagnosis of OSCC, selecting the appropriate operation procedure of neck dissection leading to increased survival ratio and improved quality of life for the patients.

Subcategories of patients with King-Kopetzky syndrome

King-Kopetzky syndrome (Obscure Auditory Dysfunction, OAD) has been recognized as a clinically distinct condition in audiological and ENT clinics. It is characterized by normal hearing thresholds on pure tone audiometry (PTA) but complaints of difficulties in understanding speech in the presence of background noise. In a study on 110 consecutive patients with King-Kopezky syndrome referred to the Welsh Hearing Institute, subjects were subdivided into seven subcategories based on sensitized measures of auditory dysfunction and on psychological assessment. These were: (1) middle ear dysfunction; (2) mild cochlear pathology; (3) central/medial olivocochlear efferent system (MOCS) auditory dysfunction; (4) purely psychological problems; (5) multiple auditory pathologies; (6) combined auditory dysfunction and psychological problems and (7) unknown. Different subgroups may represent different pathogenic and aetiological factors. Thus, subcategorization provides further understanding of the basis of King-Kopetzky syndrome, and hence may guide the rehabilitative management of these patients.

Electrochemical treatment of lung cancer

A pilot study of electrochemical treatment (ECT) as a therapy for 386 patients with nonsmall cell lung cancer was undertaken. There were 103 stage II cases, 89 stage IIIa cases, 122 stage IIIb cases, and 72 stage IV cases. Two ECT methods were used: For peripherally located lung cancer, platinum electrodes were inserted transcutaneously into the tumor under x-ray or CT guidance. For central type lung cancer or for those inoperable during thoracotomy, electrodes were inserted intraoperatively directly into the cancer. Voltage was 6-8 V, current was 40-100 mA, and electric charge was 100 coulombs per cm of tumor diameter. The number of electrodes was determined from the size of cancer mass, because the diameter of effective area around each electrode is approximately 3 cm. The short-term (6 months after ECT) results of the 386 lung cancer cases were: complete response (CR), 25.6% (99/386); partial response (PR), 46.4% (179/386); no change (NC), 15.3% (59/386); and progressive disease (PD), 12.7% (49/386). The total effective rate (CR + PR) was 72% (278/386). The 1, 3, and 5 year overall survival rates were 86.3% (333/386), 58.8% (227/386), and 29.5% (114/386), respectively. The main complication was traumatic pneumothorax, with an incidence rate of 14.8% (57/386). These clinical results show that ECT is simple, safe, effective, and minimally traumatic. ECT provides an alternative method for treating lung cancers that are conventionally inoperable, that are not responsive to chemotherapy or radiotherapy, or that cannot be resected after thoracotomy. Long-term survival rates suggest that ECT warrants further investigation.

Characterization of a Mycobacterium smegmatis mutant that is simultaneously resistant to D-cycloserine and vancomycin

A mutant of Mycobacterium smegmatis has been isolated that is simultaneously resistant to both D-cycloserine (D-CS) and vancomycin. Genetic complementation with a PBP4 homolog restores sensitivity to both drugs. Resistance to D-CS and vancomycin in this mutant is most likely due to a novel mechanism involving peptidoglycan assembly at the cell surface.

[Mechanism of impairment to microtubule polymerization resulting from zinc deficiency during pregnancy and lactation in mice]

To probe into the mechanism of zinc deficiency on microtubule polymerization impairment, the learning ability and the levels of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 expression in the brain of zinc deficient offsprings, maternal ICR mice were fed with experiment diets containing different levels of zinc(1, 5, 30 and 100 mg/kg) during pregnancy and lactation respectively. On the postnatal day 70 of offsprings, the learning ability and the expression of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 in the brain were examined by shuttle box and Western blot assays respectively. The results showed that the number of trials needed to reach the learning criterion for zinc deficient groups (1 and 5 mg/kg) was much higher than that for non zinc deficient groups (30 and 100 mg/kg). The levels of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 expression in the brain of zinc deficient offsprings (1 and 5 mg/kg) were lower than those in the brain of offsprings whose dams fed with zinc adequately supplied diet (30 mg/kg) and zinc supplemented supplied diet (100 mg/kg) respectively. These results suggested that the inhibition of alpha-tubulin, beta-tubulin and microtubule-associated protein 2 expression might be the most important mechanism of microtubule polymerization decline resulting from zinc deficiency, which had close relationship with brain function impairment.

Mutations in TFAP2B cause Char syndrome, a familial form of patent ductus arteriosus

Char syndrome is an autosomal dominant trait characterized by patent ductus arteriosus, facial dysmorphism and hand anomalies. Using a positional candidacy strategy, we mapped TFAP2B, encoding a transcription factor expressed in neural crest cells, to the Char syndrome critical region and identified missense mutations altering conserved residues in two affected families. Mutant TFAP2B proteins dimerized properly in vitro, but showed abnormal binding to TFAP2 target sequence. Dimerization of both mutants with normal TFAP2B adversely affected transactivation, demonstrating a dominant-negative mechanism. Our work shows that TFAP2B has a role in ductal, facial and limb development and suggests that Char syndrome results from derangement of neural-crest-cell derivatives.

[Comparison and observation on chromosome telomeric associations in human lung cancer.]

BACKGROUND

To explore the regularity of abnormal telomeric associations in cellular chromosome of human lung cancer.

METHODS

The rate of telomeric associations was detected in human lung adenocarcinoma cell line A549 , peripheral blood lymphocytes in 15 patients with lung cancer , and in patients with non-cancerous diseases and normal adults as control by chromosome preparation assay.

RESULTS

A highly significant difference in the rate of telomeric associations was found between lung cancer group and control group ( P < 0. 005) . Human lung adenocarcinoma cell line A549 had the highest rate of telomeric associations in all groups ( P < 0. 005) . Moreover , there was significant difference in the rate of telomeric associations in idiogramB , idiogram C and idiogram D between lung cancer group and control group (idiogram B , P < 0. 05 ; idiogram C , idiogram D , P < 0. 005) .

CONCLUSIONS

Compared with control group , human lung adenocarcinoma cell line A549 and lung cancer chromosome has higher telomeric associations and most of themoccured in idiogramB , idiogram C and idiogram D. It will provide worthwhile data of cell genetics for further research work on early diagnosis and prognosis in human lung cancer.

Cerebral palsy and multiple births in China

BACKGROUND

A population-based study on prevalence of cerebral palsy in multiple births has not been carried out in China. The purpose of this paper was to determine the prevalence of cerebral palsy in multiple births and to explore the influence of multiple pregnancy on cerebral palsy after controlling for birthweight.

METHODS

A cross-sectional study of cerebral palsy was carried out among 388,192 children aged <7 years in seven cities of Jiangsu province in China. Information about birthweight and plurality was obtained from routine health care records. Pediatricians at city level diagnosed all cases. All the doctors involved had taken part in a training programme held by Beijing Medical University. Stratified analysis by birthweight and its standard normal deviate was employed to compare the prevalence of cerebral palsy in multiples and singletons.

RESULTS

The prevalence of cerebral palsy for children aged <7 years in multiples was 9.7 per 1000 children (95% confidence interval [CI]: 6.5-14.0), which was 6.5 times that in singletons (95% CI: 4.4-9.3). The overall neonatal mortality rate was 60.9 per 1000 liveborn multiples, being highest (944.4 per 1000) in the 500-999 g birthweight groups. Most liveborn multiples weighing <1500 g at birth probably died from diseases related to very low birthweight prior to this study. The prevalence of cerebral palsy in multiple births was likely to be higher than that reported in developed countries for children weighing 1500-2499 g even though our data were from a cross-sectional study. When stratified by birthweight, the prevalence of cerebral palsy in multiples weighing <2500 g had tended to be lower than that of singletons in the same birthweight group. In contrast, in normal birthweight categories multiple births had a higher prevalence of cerebral palsy than singletons. When stratified by birthweight normal deviate, the prevalence of cerebral palsy in multiple births was uniformly higher than that in singletons in all birthweight strata and the prevalence of cerebral palsy among multiples appeared to be augmented as birthweight increased.

CONCLUSION

The prevalence of cerebral palsy in multiples, 9.7 per 1000 children, is 6.5 times that in singletons. Survival of low birthweight infants is lower in China than in developed countries and survival quality of Chinese children weighing 1500-2499 g needs to be further improved. In terms of birthweight multiples and singletons may be heterogeneous. It might be difficult to directly use actual birthweight specific prevalence to compare the prevalence of cerebral palsy in multiples and singletons. Birthweight normal deviate specific prevalence of cerebral palsy suggests that multiple pregnancy is an independent risk factor for cerebral palsy in all birthweight groups. Multiples are in adverse circumstances very early in gestation and as the foetus matures the risk of cerebral palsy increases.

Fast algorithm for chirp transforms with zooming-in ability and its applications

A general fast numerical algorithm for chirp transforms is developed by using two fast Fourier transforms and employing an analytical kernel. This new algorithm unifies the calculations of arbitrary real-order fractional Fourier transforms and Fresnel diffraction. Its computational complexity is better than a fast convolution method using Fourier transforms. Furthermore, one can freely choose the sampling resolutions in both x and u space and zoom in on any portion of the data of interest. Computational results are compared with analytical ones. The errors are essentially limited by the accuracy of the fast Fourier transforms and are higher than the order 10(-12) for most cases. As an example of its application to scalar diffraction, this algorithm can be used to calculate near-field patterns directly behind the aperture, 0 < or = z < d2/lambda. It compensates another algorithm for Fresnel diffraction that is limited to z > d2/lambdaN [J. Opt. Soc. Am. A 15, 2111 (1998)]. Experimental results from waveguide-output microcoupler diffraction are in good agreement with the calculations.

[Effects of pre-heating on the sensitivity of K562 cell to tumor necrosis factor-alpha]

In order to study the effects of pre-heating on the sensitivity of cells to tumor necrosis factor-alpha (TNF-alpha), the K562 cells were pre-heated at 40 degrees C for different times to induce heat shock protein 70 (HSP70). To observe the effects of TNF-alpha concentration on the sensitivity of pre-heated cells, cells were pre-heated for 60 min and treated with TNF-alpha (50, 100, 200 and 400 U/ml) for 16 hours, and the cells vitalities were detected by MTT. In order to observe the effect of pre-heating time on the sensitivity of cells to TNF-alpha, the pre-heated cells were treated with 100 U/ml TNF-alpha for 24 hours. The levels of HSP70 were tested by reversed transcription-PCR(RT-PCR). The results showed that HSP70 could be induced by pre-heating, and reached its top level after 120 mins, and the sensitivity of non-heated cells to TNF-alpha was lower than that of pre-heated cells. To 100 U/ml TNF-alpha, the sensitivity was lowest after the cells were pre-heated for 120 min. The results suggested that pre-heated could induce the expression of HSP70 and inhibit the sensitivity of cell to TNF-alpha, the mechanism may be involved with the overexpression of HSP70.

Dominant negative down-regulation of endotoxin-induced tumor necrosis factor alpha production by Lps(d)/Ran

We recently showed that adenoviral transfer and expression of the Lps(d)/Ran gene isolated from endotoxin-resistant C3H/HeJ mice could protect endotoxin-sensitive mice from endotoxic shock. Elevation of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha), is thought to be essential for the development of septic shock. To investigate the extent to which Lps(d)/Ran affects TNF-alpha production, we transduced primary macrophages from endotoxin-sensitive and -resistant mice with adenoviral vectors expressing the wild-type and the mutant Lps/Ran cDNAs and other control genes, and compared the amount of TNF-alpha produced by these various transduced macrophages. Successful transfer and expression of Lps(d)/Ran cDNA in endotoxin-sensitive C3H/HeOuJ macrophages reduced TNF-alpha production upon lipopolysaccharide (LPS) stimulation, as compared with macrophages transduced with vectors expressing the wild-type Lps(n)/Ran cDNA, the green fluorescent protein gene, or the lacZ gene. On the other hand, successful transfer and expression of the wild-type Lps(n)/Ran cDNA in primary macrophages from endotoxin-resistant C3H/HeJ mice failed to induce TNF-alpha production to any significant extent unless a very high LPS concentration was used. Given our previous demonstration that Lps(n)/Ran functions effectively in restoring LPS responsiveness in B cells from C3H/HeJ mice, we conclude that Lps/Ran is involved in a CD14-independent signal transduction pathway. This dominant negative down-regulation by Lps(d)/Ran on TNF-alpha production by macrophages and probably other innate immune responses may be key to the development of an effective gene therapy for endotoxic or septic shock.

Heck reactions of iodobenzene and methyl acrylate with conventional supported palladium catalysts in the presence of organic and/or inorganic bases without ligands

The vinylation of iodobenzene with methyl acrylate has been studied with several supported palladium catalysts in N-methylpyrrolidone in the presence of triethylamine and/or sodium carbonate. The reaction can be performed in air without any solubilizing or activating ligands. It was found that significant amounts of palladium leach out into the solvent and these dissolved Pd species essentially catalyze the reaction. It is interesting, however, that almost all the palladium species in the solution can redeposit onto the surface of the supports after the reaction has been completed (at 100% conversion of iodobenzene). Thus, the catalysts were recyclable without loss of activity. The use of both inorganic and organic bases is very effective in the promotion of the palladium redeposition as well as in the enhancement of the reaction rate. For Heck reactions with bromobenzene and chlorobenzene it was found that the use of triethylamine and sodium carbonate increases the selectivity of the Heck coupling product (benzene is also produced for these two substrates), but the mixed bases do not affect the overall rate of reaction as much.

The role of a family history in King Kopetzky Syndrome (obscure auditory dysfunction)

King Kopetzky Syndrome (KKS) is a common condition in which individuals with normal audiograms complain of hearing difficulties, particularly in noisy places. Several studies have shown many patients with KKS to have a family history of hearing problems. In 82 consecutive patients with KKS and normal middle ear function, we compared the performance of those with and without a family history of hearing impairment on a number of sensitized tests. Those with a family history were more likely to have notches on Audioscan testing (p < 0.005) and these notches were broader than those found in patients with no family history (p < 0.05). There was also a tendency for those with a family history to be more likely to have notches on DPOAEs (p < 0.07), and the reproducibility of the TOAEs was poorer in those with a family history. Psychological testing showed males with a family history to have higher scores on free-floating anxiety (p < 0.01) and obsessionality (p < 0.05).

Simulation modeling of nuclear steam generator water level process--a case study

Simulation modeling of the nuclear steam generator (SG) water level process in Qinshan Nuclear Power Plant (QNPP) is described in this paper. A practical methodology was adopted so that the model is both simple and accurate for control engineering implementation. The structure of the model is in the form of a transfer function, which was determined based on first-principles analysis and expert experience. The parameters of the model were obtained by taking advantage of the recorded historical response curves under the existing closed-loop control system. The results of process dimensional data verification and experimental tests demonstrate that the simulation model depicts the main dynamic characteristics of the SG water level process and is in accordance with the field recorded response curves. The model has been successfully applied to the design and test of an advanced digital feedwater control system in QNPP.

A data preprocessing framework for supporting probability-learning in dynamic decision modeling in medicine

Data preprocessing is needed when real-life clinical databases are used as the data sources to learn the probabilities for dynamic decision models. Data preprocessing is challenging as it involves extensive manual effort and time in developing the data operation scripts. This paper presents a framework to facilitate automated and interactive generation of the problem-specific data preprocessing scripts. The framework has three major components: 1) A model parser that parses the decision model definition, 2) A graphical user interface that facilitates the interaction between the user and the system, and 3) A script generator that automatically generates the specific database scripts for the data preprocessing. We have implemented a prototype system of the framework and evaluated its effectiveness via a case study in the clinical domain. Preliminary results demonstrate the practical promise of the framework.

The seismocardiogram as magnetic-field-compatible alternative to the electrocardiogram for cardiac stress monitoring

Seismocardiography (SCG) is a methodology derived from the field of seismology to measure non-invasively compression waves generated by myocardial motion. The use of SCG is proposed here as method to monitor cardiac function during stress testing and magnetic resonance imaging (MRI). It is shown that recording of the seismocardiogram in subjects undergoing an MRI study is not compromised by flow-induced electrical voltages that can severely distort the electrocardiogram. Electromagnetic compatibility of the seismocardiograph device with the MRI scanner hardware was tested. Experiments in an animal model proved that changes in the SCG waveform during different levels of LAD stenosis correlate with the changes seen in LV function with cine MRI. The changes in the SCG waveform characteristic for the onset of ischemia were observed almost immediately after the creation of a flow-limiting stenosis. This novel application of SCG to monitor changes in peak acceleration from cardiac blood flow and wall motion may represent a solution to the long-standing and important problem of monitoring patients for signs of myocardial ischemia during MRI.

[6A8 cDNA encodes A type of alpha-mannosidase]

OBJECTIVE

To find the nature of the protein encoded by 6A8 cDNA.

METHODS

In the light of that the ligand of Con A is mannoses and that the function of alpha-mannosidase is trimming of mannoses in the oligosaccharide chains of glycoproteins, COS-7 cells and CNE-2L2 cells, a cloned cell line of human nasopharyngeal carcinoma, were transfected with pRc/CMV-sense 6A8 cDNA or pRc/CMV-antisense 6A8 cDNA and the Con A binding to the cells was examined upon a lazer scan confocal microscope.

RESULTS

The data demonstrated that with transfection of pRc/CMV-sense 6A8 cDNA the binding of Con A to the cells was decreased, but the staining of the cells with mAb 6A8 was enhanced, and vise versa for the cells with transfection of pRc/CMV-antisense 6A8 cDNA.

CONCLUSIONS

The protein encoded by 6A8 cDNA might be a type of alpha-mannosidase recognized by mAb 6A8.

[Spectrophotometric determination of cinnarizine based on charge-transfer reaction]

The charge-transfer (CT) complex formed between cinnarizine as the donor and 7, 7, 8, 8-Tetracyanoquinodimethane (TCNQ) as the acceptor in acetone-methanol has been studied by spectrophotometric method. Beer's law is obeyed in the range of 0-18 microg x mL(-1) of cinnarizine. The apparent molar absorptivity of CT complex at 743 nm is 1.58 x 10(4) L x mol(-1) x cm(-1). The composition of CT complex is found to be 1 : 1 by Bent-French and Job's methods. The relative standard deviation is less than 3% (n = 10). The method has been applied to the determination of cinnarizine in tablets with satisfactory results.

Test-retest variability of distortion-product otoacoustic emissions in human ears with normal hearing

In the present study, the test-retest variability of distortion product otoacoustic emissions (DPOAEs) due to various causes has been assessed quantitatively at individual frequencies using the ILO88/92 system. The short-term variance was generally lower than 3 dB2. Changing the position and the fit of the probe may affect the level of background noise in the ear canal, which interferes with the responses of the DPOAEs mainly at low frequencies and can also influence the interaction of the resonances of the outer ear and acoustic stimuli. The long-term variance was significantly greater than short-term variance, but did not differ significantly from variance of refitting the probe. The total DPOAE variance was small across all the frequencies above 1000 Hz except for a small peak in the 2500 Hz range. This may be related to the low response amplitudes in this region. The limitation of DPOAE detection at frequencies below 1000 Hz must lead to caution in the interpretation of results in this frequency range. The magnitude of the total variance was similar to that found in audiometric studies.