background extract for the data;There are also problems arising from the fact that the transport infrastructure for inter-African trade is not adequate. Experience shows that even when tariffs have been reduced and intra-country transport links are open, the cost of transport between countries forming a cooperation arrangement tend to he high and a very high external tariff would be required to make a customs union, shift the advantage in favour of intra-sub-regional trade. There are a number of problems of an operational and institutional nature which make inter-African cooperation difficult. Some of the critical ones related to banking arrangements, information, language, costs of promotion, prices of goods to be traded and non-physical barriers to cross-border moverment of goods and services. Banking relations between various African countries are weak, particularly between French-speaking and English-speaking African countries. Trade documents in different languages make it difficult to integrate different language-speaking countries financially and economically , and it becomes difficult to exchange trade information among such countries. Lack of information is another important factor that has hindered the development of intra-regional trade. Most African countries are traditionally linked with the countries of their former colonial masters and have very few trade relationships with other African countries

subjective questions

Question 21 1. Please explain the term Coombs' positive (direct and indirect) and negative haemolytic anaemia. 2. What are the principles of the Coombs' test?

Question 22 How often is Aldomet (alpha methyldopa) associated with autoimmune haemolytic anaemia or hepatitis? Is a normal person, with a positive Coombs' test owing to previous treatment with this drug, safe to donate blood?

Question 23 What is the mechanism of priapism in sickle-cell anaemia?

Question 24 Is sickle-cell disease associated with any of the glomerular disorders?

Question 25 What is the acute chest syndrome?

Question 26 Patients with thalassaemia intermedia have recurrent leg ulcers and recurrent infections. What is the mechanism of this?

Question 27 What is the mechanism of iron absorption from iron polymaltose complex and carbonyl iron?

Question 28 Iron overload in patients with thalassaemia major should be checked by measuring the serum ferritin and hepatic iron stores. How are the hepatic iron stores measured? By liver biopsy? And does not the measurement of serum ferritin suffice?

Question 29 In the investigation for paroxysmal nocturnal haemoglobinuria (PNH), are the sucrose haemolysis test and Ham's acid serum test commonly done? What are the principles behind these tests?

Question 30 Why isn't the blood of polycythaemia vera patients, after repeated phlebotomies, used for transfusion purposes? Although it is a premalignant condition, the red cells do not contain a nucleus and thus transfusion of only pure red blood cells (RBCs) would be a great benefit