A 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).

BACKGROUND AND OBJECTIVES: 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. DESIGN AND SETTING: 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. PATIENTS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Assessment of alpha-fetoprotein in the diagnosis of hepatocellular carcinoma in Middle Eastern patients.

BACKGROUND: Alpha-fetoprotein (AFP) levels for the diagnosis of hepatocellular carcinoma (HCC) may vary by geographical region and racial background. No data exists for this test in the Middle Eastern population. In addition, there is limited data on the impact of virological status on AFP levels. METHODS: In a multicenter, case-control study involving 206 cases, 199 cirrhotic and 197 chronic hepatitis controls, we assessed the utility of AFP in the diagnosis of HCC (sensitivity, specificity, positive (PPV) and negative (NPV) predictive values, and positive likelihood ratios (LR). PPV and NPV were evaluated for three additional HCC prevalence rates (5, 10, and 20%). RESULTS: The best discriminating AFP value was 11.7 ng/ml. The sensitivity ranged from 32 to 79.5% at different AFP levels with the specificity increasing sequentially from 47.7 to 98.5%. Sensitivity of AFP at the best cut-off level for hepatitis C virus (HCV), hepatitis B virus (HBV) and non-viral etiology for HCC was 73.7, 65.6, and 59.5%, respectively. Specificity at this level for HCV, HBV, and non-viral etiology was 36.6, 30.1, and 29.4%, respectively. AFP cut-off levels of 102, 200, and 400 ng/ml showed similar sensitivity (39.8, 35.9, and 32%, respectively) and specificity (96, 98.5, and 98.5% respectively). Positive LR for AFP at >11.7, >20, >102, >200, >400 ng/ml were 2.8, 3.3, 9.9, 23.8, and 21.2, respectively. CONCLUSIONS: In cirrhotic patients, AFP has a poor screening and diagnostic value for HCC. Underlying viral etiology fails to influence the diagnostic accuracy of this test. An AFP level greater than 100 ng/ml has a high degree of specificity and may be used as a confirmatory test.