role of rapid testing and clinical decision in the diagnosis of human influenza A H1N1 infection

To evaluate the role of the rapid influenza diagnostic test [RIDT] and clinical decision in the diagnosis of H1N1. In November 2009, 290 suspected influenza patients were examined for H1N1 during an outbreak in Riyadh, Saudi Arabia. Nasopharyngeal swabs were analyzed using Directigen EZ Flu A+B kit. Monoclonal anti-human influenza A/B and reverse transcription- polymerase chain reaction [RT-PCR] were used. Positive and negative controls were used in each run of specimens. Validity indices were calculated for RIDT and clinical diagnostic criteria. The sensitivity and specificity of RIDT were 40.5% [95% confidence interval [CI]: 33.0-48.5], and 94.5% [95% CI: 88.6-97.6]. The sensitivity of clinical decision was 66.3% [95% CI: 58.4-73.4], and the specificity was 65.4% [95% CI: 56.3-73.4]. The sensitivity of clinical decision was higher in early presenters [79.2%; 95% CI: 57.3-92.1]. The RIDT sensitivity was higher in younger patients [48.4%; 95% CI: 35.7-61.3]. The positive predictive value [PPV] was 90.4% [95% CI: 80.7-95.7] for RIDT, and 71.1% [95% CI: 63.1-78.0] for clinical decision. The PPV for RIDT was greater for older [94.7%; 95% CI: 80.9-99.1] and late [90.7%; 95% CI: 76.9-97.0] presenters. The adjusted odds ratio for clinical decision was significant for cough, headache, and fatigue. The RIDT can be useful in epidemics and high prevalence areas, whereas clinical decision, and RT-PCR complement the diagnosis of H1N1 in any setting

Changing epidemiology of tuberculosis detected by an 8-year retrospective laboratory study in a tertiary teaching hospital in central Saudi Arabia

To study the laboratory diagnosis of tuberculosis [TB], and relate the findings to its epidemiology in Central Saudi Arabia. This retrospective study was carried out at the Department of Pathology/Microbiology, King Khalid University Hospital, Riyadh, Kingdom of Saudi Arabia between January 2003 and December 2010. Data were retrieved from the hospital information system on laboratory findings. After adjustment, 9,405 specimens were studied. The specimens were stained by Ziehl-Neelsen [ZN], auramine-rhodamine, and cultured in Bactec alert 960, and Lowenstein-Jensen media. Mycobacterium tuberculosis [M. tuberculosis] complex and non-tuberculous mycobacteria were differentiated by ProbTec system and p-nitrobenzoate medium. The BACTEC MGIT 960 SIRE kit was used for susceptibility testing. A total of 568 [6%] specimens grew M. tuberculosis complex, and 87% were from Saudis with an incidence rate of 55.6/100,000 of TB. Time to positive growth in the Bactec liquid medium was directly related to the acid fast bacilli smear load. Most of the positive patients were from the 18-35 years age group. The percentage of multidrug resistance was 0.7%. Most patients [87%] were Saudis showing an incident rate of 55.6/100,000. An increase of TB cases was noticed in the 18-35 age group. Resistance to isoniazid was 10.6%, 1% to Rifampicin, 2-8% to Ethambutol, and streptomycin was 6%

validation study comparing the sensitivity and specificity of the new Dr. KSU H1N1 RT-PCR kit with reAl time RT-PCR for diagnosing influenza A [H1N1]

A new test [Dr. KSU H1N1 RT-PCR kit] was recently developed to provide a less expensive alternative to reAl time reverse transcriptase-polymerase chain reaction [RT-PCR]. We report the findings of a validation study designed to assess the diagnostic accuracy, including sensitivity and specificity, of the new kit, as compared to reAl time RT-PCR. Cross-sectional validation study conducted from 18-22 November 2009 at a primary care clinic for H1N1 at a tertiary care teaching hospital in Riyadh. Nasopharyngeal swab samples and data on socio-demographic characteristics and symptoms were collected from 186 patients. Swab samples were sent to the laboratory for testing with both reAl time RT-PCR and the new Dr. KSU H1N1 RT-PCR kit. We measured the sensitivity and specificity of the new test across the entire sample size and investigated how these values were affected by patient socio-demographic characteristics and symptoms. The outcomes of the two tests were highly correlated [kappa=0.85; P<.0001]. The sensitivity and specificity of the new test were 99.11% and 83.78%, respectively. The sensitivity of the new test was affected only minimally [96%-100%] by patient characteristics and number of symptoms. On the other hand, the specificity of the new test varied depending on how soon patients were tested after onset of symptoms [100% specificity when swabs were taken on the first day of the symptoms, decreasing to 75% when swabs were taken on or after the third day]. The specificity of the new test also increased with increasing body temperature. The new test seems to provide a cost-effective alternative to reAl time RT-PCR for diagnosing H1N1 influenza. However, further testing may be needed to verify the efficacy of the test in different settings and communities