Whilst reviewing a patient's drug card you notice that you prescribed the wrong dose of atenolol when the patient was initially clerked. Instead of 25mg atenolol od you prescribed 50mg atenolol od. She has received the incorrect dose on two occasions. On examining Mrs Smith you note her blood pressure and pulse are normal. Mrs Smith has a past history of anxiety and describes herself as a 'worrier'.
What is the most appropriate action?
Correct Answer B: In this scenario the patient appears to have come to no harm following the error. This should not however change your approach to the situation. The patient should be informed of what has happened, an apology should be made and reassurance give that there appears to be no ill effects.
By completing a clinical incident form you add to a body of data which may in the long term change to practice.
An entry to your e-portfolio at least shows that you both acknowledge and are willing to learn from the error. The yellow card system is intended to report side-effects from drugs rather than prescription errors and hence is fairly pointless.
The dose of a drug a patient takes should be based on clinical need rather than a reluctance to acknowledge an error.
A 25-year-old man is counselled regarding the genetics of Huntington's disease.
Which one of the following best describes the concept of anticipation?
Correct Answer B: Anticipation in trinucleotide repeat disorders = earlier onset in successive generations.
Difficult question. In the exam both B and C were given as choices. The 'classic' definition of anticipation is earlier onset in successive generations. However, in most cases, an increase in the severity of symptoms is also noted. If both options are presented then B should be chosen, as this represents the more accepted definition of anticipation. What do you think?
Trinucleotide repeat disorders: Trinucleotide repeat disorders are genetic conditions caused by an abnormal number of repeats (expansions) of a repetitive sequence of three nucleotides. These expansions are unstable and may enlarge which may lead to an earlier age of onset in successive generations - a phenomenon known as anticipation*. In most cases, an increase in the severity of symptoms is also noted.
Examples - note dominance of neurological disorders:
*Friedreich's ataxia is unusual in not demonstrating anticipation.
Tamsulosin is a:
Correct Answer D:
Adrenoceptor antagonists: 1- Alpha antagonists:
2- Beta antagonists:
Carvedilol and labetalol are mixed alpha and beta antagonists.
A 30-year-old man is referred to ophthalmology due to deteriorating visual acuity. Both his brother and uncle on his mother's side have developed similar problems.
What is the most likely mode of inheritance of his condition?
Correct Answer C: This first clue is the nature of the disease - many of the inherited eye disorders such as retinitis pigmentosa and ocular albinism are inherited in an x-linked recessive pattern. For this disorder to be autosomal recessive both the patient's parents would need to be carriers (heterozygous) as well as both his maternal aunt and uncle. Even for common autosomal recessive disorders such as cystic fibrosis the carrier rate is around 1 in 25 making this statistically less likely.
X-linked recessive: In X-linked recessive inheritance only males are affected. An exception to this seen in examinations are patients with Turner's syndrome, who are affected due to only having one X chromosome. X-linked recessive disorders are transmitted by heterozygote females (carriers) and male-to-male transmission is not seen. Affected males can only have unaffected sons and carrier daughters.
Each male child of a heterozygous female carrier has a 50% chance of being affected whilst each female child of a heterozygous female carrier has a 50% chance of being a carrier.
The possibility of an affected father having children with a heterozygous female carrier is generally speaking extremely rare. However, in certain Afro-Caribbean communities G6PD deficiency is relatively common and homozygous females with clinical manifestations of the enzyme defect are seen.
A new test to screen for ovarian cancer in patients with a positive family history is tested on 920 patients. The test is positive in 16 of the 20 patients who are proven to have ovarian cancer. Of the remaining patients, only 10 have a positive test.
What is the negative predictive value of the new test?
A contingency table can be constructed from the above data, as shown below:
The negative predictive value = TN / (TN + FN) = 890 / (890 + 4) = 890/894
Screening test statistics: It would be unusual for a medical exam not to feature a question based around screening test statistics. The available data should be used to construct a contingency table as below: TP = true positive; FP = false positive; TN = true negative; FN = false negative.
The table below lists the main statistical terms used in relation to screening tests:
Positive and negative predictive values are prevalence dependent. Likelihood ratios are not prevalence dependent .
Click to expand