High‐frequency ventilation with the Dräger Babylog 8000plus: measuring the delivered frequency

Background: Ventilator frequency is one of the determinants of tidal volume delivery during high‐frequency ventilation. Clinicians increasingly use data on ventilator displays to inform their decisions. Aim: To measure the frequencies delivered by the Dräger Babylog 8000plus ventilator when used in high‐frequency mode. Methods: Ventilator waveforms using a test lung were recorded at the full range of settings 5–20 Hz using Spectra software at 1000 Hz. The changes in frequency produced by a 1‐ Hz change in set frequency were calculated. Actual and displayed frequencies were compared. Results: For settings up to 12 Hz, median (range) difference between set and delivered frequencies was 0 (?0.4 to +0.1) Hz. Above 12 Hz, delivered frequency varied by ?0.3 (?1.9 to +0.3) Hz. For 1‐ Hz changes in frequency settings, in the range 5–12 Hz, 1‐ Hz changes produced a change in delivered frequency of 1.0 (0.6–1.4) Hz. Above 12 Hz, the corresponding changes were 0.7 (0–2.9) Hz. The ventilator displays the set frequency during operation rather than the delivered frequency. Conclusion: At 12 Hz and below, the differences between set and delivered frequencies were relatively small compared with those at 13 Hz and higher. Above 13 Hz, the difference between set and delivered frequencies was up to 2.9 Hz. Some frequency setting changes did not result in a change in delivered frequency.     

Reliable high risk HPV DNA testing by polymerase chain reaction: an intermethod and intramethod comparison

BACKGROUND: The development of a reproducible, sensitive, and standardised human papillomavirus (HPV) polymerase chain reaction (PCR) test is required to implement HPV testing in cervical cancer screening programmes and for triaging women with mild to moderate dysplasia. AIMS: To determine the intermethod agreement between different GP5+/6+ and MY09/11 PCR based protocols for the detection and typing of high risk (HR) HPV DNA in cervical smears and to assess the intramethod reproducibility of the GP5+/6+ PCR enzyme immunoassay (EIA) for HR-HPV detection. METHODS: For the intermethod comparison, crude aliquots of 20 well characterised cervical smears comprising five HPV negative samples, and six and nine samples containing single and multiple HPV infections, respectively, were coded and sent from reference laboratory (A) to three other laboratories. One of these (laboratory B) used the GP5+/6+ PCR-EIA and was provided with standard protocols. Another laboratory (C) used GP5+/6+ PCR combined with sequence analysis and type specific PCR, whereas two laboratories (D and E) used MY09/11 PCR followed by restriction fragment length polymorphism (RFLP) analysis for the detection and typing of HR-HPV. The intramethod agreement of GP5+/6+ PCR-EIA was analysed in a subsequent study with four other laboratories (F to I) on crude aliquots of 50 well characterised cervical smears, consisting of 32 HR-HPV positive and 18 HPV negative samples. Standardised protocols, primers, and probes were also provided by the reference laboratory for HR-HPV detection. RESULTS: In the intermethod comparison, pairwise agreement of the different laboratories with reference laboratory A for the detection of HR-HPV varied between 75% and 100% (kappa values: 0.5 to 1). Typing data revealed a broader range in pairwise agreement rates between 32% and 100%. The highest agreement was found between laboratories A and B using standardised protocols and validated reagents. In the intramethod evaluation, pairwise comparison of the laboratories F to I with reference laboratory A revealed excellent agreement rates from 92% to 100% (kappa values: 0.88 to 1.0) with an overall sensitivity of 97.5% (195/200) and specificity of 99.5% (199/200). CONCLUSIONS: The detection of HR-HPV as a group is highly reproducible with GP5+/6+ PCR-EIA provided that standardised protocols and validated reagents are used.     

Human papillomavirus is a necessary cause of invasive cervical cancer worldwide

A recent report that 93 per cent of invasive cervical cancers worldwide contain human papillomavirus (HPV) may be an underestimate, due to sample inadequacy or integration events affecting the HPV L1 gene, which is the target of the polymerase chain reaction (PCR)-based test which was used. The formerly HPV-negative cases from this study have therefore been reanalysed for HPV serum antibodies and HPV DNA. Serology for HPV 16 VLPs, E6, and E7 antibodies was performed on 49 of the 66 cases which were HPV-negative and a sample of 48 of the 866 cases which were HPV-positive in the original study. Moreover, 55 of the 66 formerly HPV-negative biopsies were also reanalysed by a sandwich procedure in which the outer sections in a series of sections are used for histological review, while the inner sections are assayed by three different HPV PCR assays targeting different open reading frames (ORFs). No significant difference was found in serology for HPV 16 proteins between the cases that were originally HPV PCR-negative and -positive. Type-specific E7 PCR for 14 high-risk HPV types detected HPV DNA in 38 (69 per cent) of the 55 originally HPV-negative and amplifiable specimens. The HPV types detected were 16, 18, 31, 33, 39, 45, 52, and 58. Two (4 per cent) additional cases were only HPV DNA-positive by E1 and/or L1 consensus PCR. Histological analysis of the 55 specimens revealed that 21 were qualitatively inadequate. Only two of the 34 adequate samples were HPV-negative on all PCR tests, as against 13 of the 21 that were inadequate ( p< 0·001). Combining the data from this and the previous study and excluding inadequate specimens, the worldwide HPV prevalence in cervical carcinomas is 99·7 per cent. The presence of HPV in virtually all cervical cancers implies the highest worldwide attributable fraction so far reported for a specific cause of any major human cancer. The extreme rarity of HPV-negative cancers reinforces the rationale for HPV testing in addition to, or even instead of, cervical cytology in routine cervical screening. Copyright © 1999 John Wiley & Sons, Ltd.     

The Aptima HPV Assay Fulfills the Cross-Sectional Clinical and Reproducibility Criteria of International Guidelines for Human Papillomavirus Test Requirements for Cervical Screening

The Aptima HPV assay (Hologic Gen-Probe, San Diego, CA) is an FDA-approved assay for detecting human papillomavirus (HPV) E6/E7 mRNA from 14 high-risk HPV types. This study evaluated the clinical performance of the Aptima HPV assay for cervical intraepithelial neoplasia of grade 2 or worse (CIN2+), relative to the high-risk HPV GP5+/GP6+ PCR, in a cross-sectional clinical equivalence analysis using the noninferiority score test with cervical samples from population-based screening, i.e., 69 cervical scraping samples from women with CIN2+ and 843 from women without evidence of CIN2+. In addition, intralaboratory reproducibility over time and interlaboratory agreement of the Aptima HPV assay results were assessed with another set of 548 cervical samples. The Aptima HPV assay showed a clinical sensitivity for CIN2+ of 94.2% (95% confidence interval [CI], 85.5 to 97.8%) and a clinical specificity for CIN2+ of 94.5% (95% CI, 92.8 to 95.9%); by comparison, these figures were 97.1% (95% CI, 89.1 to 99.3%) (67/69 samples) and 93.6% (95% CI, 91.7 to 95.0%) (785/839 samples), respectively, for GP5+/GP6+ PCR. The clinical sensitivity and specificity of the Aptima HPV assay were noninferior to those of GP5+/GP6+ PCR (P = 0.039 and 0.00016, respectively). In addition, high reproducibility of the Aptima HPV assay, as reflected by the intralaboratory reproducibility over time of 96.0% (95% CI, 94.4 to 97.3%) (526/548 samples; kappa = 0.89) and interlaboratory agreement of 96.7% (95% CI, 95.4 to 98.1%) (531/548 samples; kappa = 0.91), was found. Altogether, these data show that the Aptima HPV assay meets the cross-sectional clinical and reproducibility criteria of the international guidelines for HPV test requirements for cervical screening. Longitudinal data are needed to ensure that the long-term negative predictive value of this mRNA assay is similar to those of validated HPV DNA tests.     

The Effect of Functional Pelvic Tilt on the Three-Dimensional Acetabular Cup Orientation in Total Hip Arthroplasty Dislocations

BackgroundAnterior and posterior pelvic tilt appears to play a role in total hip arthroplasty (THA) stability. When changing from the standing to the sitting position, the pelvis typically rotates posteriorly while the hips flex and this affects the femoro-acetabular positions. This case-control study compares changes in 3-D acetabular cup orientation during functional pelvic tilt between posterior THA dislocations vs stable THAs.MethodsStanding and sitting 3-D cup orientation was compared between fifteen posterior dislocations vs 233 prospectively followed stable THAs. 3-D cup orientation was calculated using previously validated trigonometric algorithms on biplanar radiographs. Those algorithms combine the angles in the three anatomical planes (coronal inclination, transverse version, and sagittal ante-inclination) in the standing position with the change in sagittal pelvic tilt from standing to sitting to calculate the 3-D orientation in the sitting position.ResultsThe standing cup orientation of the dislocated THAs was only characterized by a lower coronal inclination (P = .039). Compared with the controls, from standing to sitting, they showed less posterior pelvic tilt (P < .001). This led to a significant lower coronal inclination (P < .001) and sagittal ante-inclination (P < .001) in the sitting position but similar transverse version (P = .366).ConclusionsComparing posterior THA dislocations to stable THAs, there is a lower increase of all three orientation angles from standing to sitting. This leads to a decreased sitting coronal inclination and sagittal ante-inclination which may lead to an increased risk of impingement ensued by THA instability. By contrast, the transverse version was not significantly different in both positions. This confirms the importance of biplanar data on functional cup orientation.Level of EvidenceDiagnostic, Level III.