The analysis of the determinants of the demand for health care is important for the formulation of policies and strategies of the health system. Income is undoubtedly one of the most important determinants of demand for health care; particularly in the current context, where TB patients are rather/predominantly recruited from the poorest in society (Nana et al., 2014). Increasing fees can have a negative impact on health services utilization (Lagarde, 2011). Even as there is additional motivation for the personnel of DTC in charge of TB patients by the NTP, in the current context of partial fee exemptions of TB treatment (lab exams paid but medication free), it has been proved that fee exemptions have negative effects on provider motivation and quality of services (Hatt, 2013). Socio-cultural factors, long distances to health facilities and poor quality of care at health facilities have been identified as barriers to utilization of institutional health facilities (Wilunda, 2014).
Besides the direct costs related to medical care, there is another group of determinants of the demand for health care, such as the opportunity costs caused by the disease that may increase the cost of medical treatment. Generally, the health system emphasizes its policy in bringing health facilities closer to the needy population. Several models of spatial competition in the context of location theory take into account the distance between the consumer and goods. Hotelling (1929) and Salop (1979) showed the distance as a factor influencing consumer choice: the consumer will tend to prefer the product that is close to him if he believes that he has the same satisfaction like other products. Nevertheless, the distance can also be understood as the accessibility to a good base on the socioeconomic level of the patient. Landcaster (1979) goes further and sees the distance not only as the geographical point but as a set of product-specific features, characteristics such that any consumer can identify himself as close to or not, according to its appreciation and accessibility to this product.
In the context of large cities such as Douala, where several health facilities (HF) “compete”, two models of spatial distribution are possible: a linear distribution, where HF are located in a straight line (Hotelling, 1929) or a circular distribution of HF around patients (Salop 1979). Those two models are implemented in the spatial distribution of HF lodging DTC in Douala, maybe as an artefact, not as result of a conscious distribution policy. A linear model is observed in the peripheral zones, the East and the West entrance of the city and the circular distribution in the urban center. The circular model delivers best results: Patients living in outlying areas of the city preferred seeking treatment in the urban center, although there are HF not far from their homes. The reverse movement is not observed in patients residing in the urban center, where the DTC are distributed circularly.
Patients might be attracted to city center because, considering HFs located there as perfect substitutes, a patient, depending on the idea he/she has of the health facilities, could be embarrassed for the choice of the HF and therefore decide to seek treatment in one or the other, with the possibility to go elsewhere in case of non-availability or long queue. On the other hand, because of the supply induced demand phenomenon, which is a specific feature of health economics, the increase in the supply of health infrastructure is driven by an increase in the demand for health care by patients (Richardson J. & Peacock S.; 2006) which explains the high demand of concentrated health facilities in the urban center.
Whereas, in peripheral areas where a long distance between the HFs is observed, a patient trapped in long queues could not have an alternative solution, especially if it turns out he/she is financially disabled: which characterizes TB patients (Nana et al., 2014). It has been proved that patients attending HF located in the periphery of Douala are those who live or spend most of their time there, such as housewives and housekeepers.
It emerges from our study that TB patients with high level of education, relatively rich, therefore workers, are among those seeking treatment in the city center, whatever their residence. On the other hand, as in many cities, a large number of inhabitants of Douala converge every day to the urban center where they work. If their health can allows them to go about their daily occupation they might avoid the opportunity costs: it might be less expensive to attend a HF in the center – when they are already working there than going back and search in their HA, especially since opening/closing hours play their role.
According to these results, in the absence of regulations on the conditions of reception and referral of patients, the concentration of health facilities in the urban center and industrial zones, with a few low-level health facilities in the periphery is the best strategy for the creation of HF in large cities.
From the supply-side, the quality of care provided by health personnel significantly influence the demand. This quality can be perceived by the reception, the availability of medical doctors and nurses or medicines of good quality. Under these conditions, poor quality reception of patients and the non-availability of conscious and qualified medical staff may discourage patients to return to a health facility. He/she might even advise his/her relatives and neighborhood against (Nana et al, 2013). Indeed, the patient, far from being a passive health consumer, is always in the search for best quality of caregivers and health facility to take care of his/her illness.
Good quality of health care in a HF should result in an important number of patients seeking a medical care in this HF, assuming that costs are the same for all HF located in the same geographic area, which is the case for TB health care in DTCs, and that, in case of good appreciation of a HF, the total number of patients attending the DTC of this HF will be equal or greater than the expected one. But the ratio of the number of patients seeking care in the DTC over the expected number (considered here as a measure of supply) varies significantly.
By focusing on the size of the population living in a geographic area to create a DTC, the health system didn't consider the daily migration of population in urban cities, to get to their workplace. It also conceives the health care offer to TB patients, as a market of pure and perfect competition, a form of market in which all hospitals produce an homogeneous “good” (health), consumers (patients) and the producers of the "good" (DTC) are informed, bear no transaction cost and have no inflation on the price. Then, each patient, aware of the homogeneity of supply would therefore not have to brave the distance, with the resulting price to be cured elsewhere if there is a DTC close to his residence. Then almost all patients who are taken care by each DTC should reside its immediate surroundings. Which is an ideal in economic theory (Ari Mwachofi, 2011) and far from the realty. Figure 2 shows a situation almost opposite to this theory in the city of Douala: the supply of health care for TB patients in the city of Douala is not perceived as a perfectly competitive market.
Many markets are characterized by monopolistic competition. The HF possesses market power, the power to set a price above marginal cost, although their economic profits remain zero. In Douala, patients consider different HF' label as imperfect substitutes. Thus, rather than comparing the DTC as such, the patient's preference based on the DTC features he has of the HF which houses the DTC.