Development and Validation of a Customer Satisfaction Measuring Instrument With Laboratory Services at The University Hospital of Kinshasa

Background: In clinical laboratory, monitoring customers’ satisfaction is an important indicator of the quality management system and required by laboratory quality standards, such as ISO 15189: 2012 and ISO17025: 2017. However, there is no reliable and valid scale to measure clinical laboratory customers’ satisfaction in Democratic Republic of the Congo. In this article, an instrument for measuring customer satisfaction with clinical laboratory services is developed and validated. Methods: In order to develop a reliable and valid measurement tool, the general methodological approach recommended by Churchill was followed. Principal component analysis (PCA) with varimax rotation was used to study the dimensionality of the construct. The developed questionnaire was checked for reliability and validity using exploratory and conrmatory analysis. The reliability checks were done using the internal consistency reliability by analyzing the Cronbach’s Alpha, composite reliability and Jöreskog Rhô values. Conrmatory Factor Analysis (CFA) was used to determine whether the hypothesis of the conceptual framework is acceptable in measuring customer satisfaction. Results: The PCA results showed a three-dimensionality of Customer Satisfaction. Cronbachs alpha coecients (0.983, 0.981 and 0.981), Jöreskog Rhô (0.973, 0.970 and 0.967) and composite reliability values (0.95, 0.92 and 0.93) of the latent variables were greater than 0.9, which conrms the very high reliability of the model. Indicator loadings were all greater than the threshold of 0.7 or higher. Also, all the latent variables have average variance extracted (AVE) greater than 0.5, therefore, convergent validity has been achieved. Both the Maximum Shared Variance (0.195, 0.297 and 0.234) and the Average Shared Variance (0.805, 0.703 and 0.766) were lower than the AVE (0.897, 0.839 and 0.875) for all the constructs in the scale. Therefore, Discriminant validity has been achieved. Fit indices used to assess CFA and structural equation model were found to be at an acceptable level for the two-factor model where chi-square/df was 1.6, p=0.476, GFI =

behind processes that deviate from procedures or are not satisfactory to customers so that proper corrective and preventive action can be initiated (Zelalem A. et al., 2013).
Assessing customer satisfaction is an important process in the laboratory's continuous quality improvement cycle (CQI) program (Donna L, 2015). The Joint Commission on Accreditation of Healthcare Organizations and the College of American Pathologists (CAPs) give accreditation to clinical laboratory programs. The CAPs require the healthcare facility to measure customer satisfaction with the laboratory services every two years. Hence, in several studies performed by Young, R. K and Teklemariam, Z, the overall customer satisfaction score was 70.5% and 87.6%, respectively (Sehr C. et al., 2017). However, no such study has been performed in Democratic Republic of the Congo (DRC) till now because of the absence of a performant measuring instrument. This suggests that there is a need to build an effective tool which would measure customer satisfaction with laboratory services in DRC. The main purpose of this study is to develop a theoretical and operational instrument for measuring customer satisfaction with clinical laboratory services. The speci c aim of this study is to present the four ndings related to the construct validity of the newly developed instrument measuring customer satisfaction. The ndings include: (a) dimensionality of the instrument, (b) reliability of the instrument, (c) validity of the construct, and (d) con rmation of the structure conceptual framework.
The paper begins with a literature review of quality of service and customer satisfaction, then explains the methodology employed, followed by the research results and ndings' discussion. Some limitations of the present work and some possible directions for future investigation are then discussed. Finally, the paper ends with key conclusions and managerial implications of the study.

Literature review
The lack of consensus on a de nition of satisfaction has created serious problems for customer satisfaction research. First, developing context-speci c items becomes di cult given the fact that the conceptual de nition of customer satisfaction is not clear. Therefore, most researches use a single-item rating scale to measure customer satisfaction. Single-item scales do not provide su cient content domain sampling of complex constructs and are generally believed to be unreliable, since they do not allow internal consistency to be calculated (Nunnally, J. C., 1978). Furthermore, Single-item measures provide no guidance to respondents or researchers in interpreting the exact meaning of satisfaction. Consequently, developing multiple-item measures to resolve the measurement di culties caused by singleitem measures is highly recommended (Churchill, G. A., Jr., 1979).
Second, the lack of de nitional and measurement standards of customer satisfaction limits theory development in this eld, weakens the explanation power of any new theories, and con nes the generalization of any empirical ndings (Wang YS et al., 2001).
Previous researchers have indicated that service quality is a precursor of customer satisfaction (Poranki KR et al., 2015).
SERVQUAL is a method intended to measure the "quality of service" in companies; it is mainly used in the private sector. This method is the starting point for most of the work on satisfaction and quality of service (Brensinger, RP., and Douglas ML., 1990). However, there have been a number of studies that question the validity of the 5 dimensions of SERVQUAL and the uniform applicability of the method for all service areas. A number of problems with the SERVQUAL instrument are discussed in the literature. According to an analysis by Thomas P. Van Dyke, Victor R. Prybutok and Leon A. Kappelman, it appears that the use of difference scores in calculating SERVQUAL contributes to problems with the reliability, discriminant validity, convergent validity, and predictive validity of the measure (Van Dyke, T. P., et al., 1999).
Consequently, many researchers proposed that a quality measurement scale should be adapted to the speci cs of an individual service industry or even an individual service, and that a general scale shouldn't be used at all (Babakus, E. and G. W. Boller. 1992). Thus, we developed an instrument for measuring customer satisfaction through quality of service in a clinical laboratory. Methods This is a cross-sectional study conducted at the University Hospital of Kinshasa. The study population consists of all attending physicians who were present at the hospital during the study period. The main purpose of this study is to develop a theoretical and operational instrument for measuring customer satisfaction with clinical laboratory services.

Measurement tool development
In order to develop a reliable and valid measurement tool, we followed the general methodological approach recommended by Churchill (1979): we adopted Churchill's paradigm for the development of service quality measurement scales. Churchill proposed eight steps for developing better measures of marketing constructs. These eight steps are in turn: "specify domain of construct, generate sample of items, collect data, purify the measure, collect new data, assess reliability with new data, assess construct validity and nally develop norms".
After a literature review, we generated a structured questionnaire including SERVQUAL items and other items from customer verbal received complaints. We developed this questionnaire using a 7-point Likert scale to prevent respondents' scores from clustering near the average: the satisfaction was measured on 7 point scale from 0 to 6 indicating the lowest (strongly disagree) and highest (strongly agree) levels of satisfaction. The instrument went through the process of checking for content validity by using a focus group followed by panels of experts before checking the construct validity. The questionnaire was then piloted with a convenient sample of 200 physicians for validity and reliability. We asked 200 physicians practitioners to pilot-test the survey before we administered it to others.
The rst step in the puri cation of the measurements is that of the dimensionality of the scales. Before proceeding to factor analyzes, we checked whether the conditions concerning the factorization of the variables were ful lled.
Principal component analysis (PCA) with varimax rotation was used to study the dimensionality of the construct. Minor adjustments were made based on the pilot testing. The self-report instrument which consisted of 14 items measuring customer satisfaction was conceptually hypothesized to have three sub-constructs, namely the Reliability of tests' results, Responsiveness of services and laboratory personnel's willingness to help. Data were then collected from 330 attending physicians in the University Hospital of Kinshasa. Trained and quali ed investigators conducted this study and distributed uni ed questionnaires to all physicians and then collected the following day. They responded to the questionnaire by writing directly on the paper. The response rate was 100%.

Research Model and Hypothesis
The following hypothesis was developed to evaluate the in uencing factors on customer satisfaction. H1: There is a positive relationship between Reliability of tests' results (TR) and customer satisfaction (CS).
H2: There is a positive relationship between Responsiveness of services (RS) and customer satisfaction (CS).
H3: There is a positive relationship between laboratory personnel's willingness to help (LP) and customer satisfaction (CS).
To examine the in uence of these three factors on customer satisfaction, the linear regression model is used. Therefore, the equation is explained as: and 100, strongly agree.

Measurement tool validation
The developed questionnaire (i.e. from pilot-test survey) was checked for reliability and validity using exploratory and con rmatory analysis. Principal component analysis (PCA) with varimax rotation was used to study the dimensionality of the construct. The Kaiser's criterion (Retain the factors whose eigenvalue is greater than 1) is chosen to determine the

Results
Before performing a factor analysis, we evaluated sample size adequacy using the Kaiser-Meyer-Olkin test of sampling adequacy (KMO). Furthermore, we assessed whether the factor analysis should be continued or not by employing Bartlett's test of sphericity.  Source: Authors' own analysis, 2020.
The scree plot con rms the choice of three components. Three clear factors emerged from this PCA as shown in Table 3. The three factors restore 93.481% of the variance explained (see table 2).
The rst factor to emerge is composed of 5 items; the second factor is made up of 5 items and the third factor is made up of 4 items. Concerning the validity or quality of the items that composed each factor, table 3 shows that each of the 14 items has a loading higher than .82. Thus, as to the items' quality, 100% of them were classi ed as excellent.
In summary, it appears that the variable "customer satisfaction" is a three-dimensional concept. Based on previous analysis, a comprehensive model for measuring customer satisfaction is presented (see gure 3) below.
After con rming the dimensionality of the scale, we prove its reliability, convergent validity and discriminant validity. Source: Authors' own analysis, 2020. Table 3 shows that indicator loadings are all greater than the threshold of 0.7 or higher. Also, table 4 shows that all the latent variables have AVE greater than 0.5, therefore, convergent validity has been achieved. Table 4 shows that the three factors registered a Cronbach's alpha score greater than .90, indicating the scale has a very high degree of reliability. The Jöreskog Rhô and Composite Reliability are greater than 0.7 which allow us to further con rm the good reliability of the construct. Furthermore, both the MSV and the ASV are lower than the AVE for all the constructs in the scale. Therefore, Discriminant validity has been achieved. Goodness of Fit Indices (GFIs) for a series of Con rmatory Factor Analysis (CFA) assessing the null, one-factor, twofactor (generated by combining in all possible ways the three theoretically de ned components) models of customer satisfaction are presented in table 5. According to Kline criteria, the two-factor model provided for a good t.   Table 6 shows that: 1. The Variance In ation Factor (VIF) coe cients are less than 4.0 (1.782, 2.559 and 2.046), which ensure there are no collinearity issues among constructs.

There is signi cant correlation between latent variables and customer satisfaction:
There is signi cant relationship between reliability of tests' results and customer satisfaction (β = .691, t = 45.79, p = .024). This nding con rms H1.
There is a signi cant relationship between laboratory personnel's willingness to help and customer satisfaction (β = .315, t = 1.69, p = .056). This nding con rms H3.

Discussion
We developed a new customer satisfaction measurement scales model and test its reliability and validity. Given that the quality of a study's results are related directly to the quality of the instrument used to collect data, it is easy to see the importance of collecting data by means of reliable and valid instrument (Andrew DPS, et al, 2001 (table 1). So the variables that the paper selects are quite suitable for factor analysis.
In factor analysis, methods of Principal Component Analysis (PCA) and varimax rotation were employed because they maximize variance and facilitate the interpretation of the constructs deduced. In view of the arbitrary nature of factor extraction, and practicability and meaningful interpretability, the following three criteria were observed in data reduction: (1) the eigenvalue was greater than 1 and there were more than 3 items in one factor; (2) factor loadings lower than 0.4 were deleted and not counted in any factor; (3) when double loadings occurred, decisions were made on meaningful interpretations. (Xu Q. and Liu J., 2018).
Based on the three criteria mentioned above, three common factors were extracted from the questionnaire. Table 2 shows that the accumulative contribution rate of three extracted common factors is 93.481%, which is bigger than 85%, i.e., the extraction of common factor is effective (Huang C, et al, 2020). Scree plot also attened out after the rst three factors. The original 14 indexes can be integrated into three common factors. According to the principle of factor analysis, the three common factors have no correlation with each other, but each common factor is highly correlated with its own contained original variables.
The three common factors extracted were named according to the items included. Table 3  The validity or quality of the items that composed each factor was also analyzed, based on Comrey and Lee classi cation. Comrey and Lee classi ed items with loadings higher or equal .71 as excellent; higher or equal .63 as very good; higher or equal .55 as good; higher or equal .45 as reasonable; and higher or equal .32 as poor (Comrey, A. L., & Lee, H. B., 1992). Thus, as to the items' quality, 100% of them were classi ed as excellent.
Questionnaires must be both reliable and valid in order for researchers to have con dence in the data collected with the instrument. Reliability, the consistency of the results obtained, concerns the extent to which the instrument yields the same results in repeated trials (Andrew DPS, et al, 2001 Factor Analysis (CFA) as part of their data analysis. There is a consensus in the literature that a score of 0.7 or higher is indicative of a construct's reliability (Hair, 2010;Nunnally, 1978;Malhotra, 2010). In this study, Cronbach alpha, Jöreskog Rhô and Composite Reliability are greater than 0.7 which con rm the good reliability of the construct (table 4).
Validity, the extent to which an instrument accurately measures the target it was designed to measure, helps a researcher determine whether or not an instrument addresses its designed purpose (Andrew DPS, et al, 2001). Testing of construct validity concentrates not only on nding out whether an item loads signi cantly on the factor it is measuring (convergent validity) but also on ensuring that it does not signi cantly load across or measure other factors (discriminant validity) (Usunier JC and Stolz J., 2016). Our results con rmed the convergent validity and discriminant validity of the constructs (table 4).
CFA were performed to compare three different models: (1) a null model; (2) a one-factor model and (3)  Thus, our three hypotheses were con rmed: the three latent variables have a positive in uence on customer satisfaction.

Limitations of the study and future research directions
This study's limitations must be acknowledged. Since this is the rst instrument of its kind to have been fully validated, there are no gold standards to evaluate criteria against it. Criterion related validity cannot be established for this instrument. The major inherent limitation is the generalization of the outcome of the study. Since the study was limited to only the University Hospital of Kinshasa and not the entire hospital market in Democratic Republic of the Congo (DRC), attempt to generalize the results should be made with caution since the study was not cross-sectional across the entire health system in DRC. Future research should, therefore, reproduce the study in other hospitals in order to con rm the results of our ndings across the health system. Because we surveyed attending physicians only, we can't con rm that the developed instrument is reliable or valid for patients. Additional research could develop another instrument for measuring customer satisfaction among patients and other customers who attain the clinical laboratory. Finally, the test-retest reliability of the instrument should be evaluated. Measures of reliability include the stability of an instrument over time. Therefore, the stability of this new instrument, including short-and long-range stability, should be further investigated using the test-retest correlation method.

Conclusion
This study has developed a new instrument for measuring customer satisfaction in clinical laboratory. Data were analyzed using exploratory factor analysis, con rmatory factor analysis and structural equation model (SEM). An instrument with a 3-factor structure shows strong potential for construct validity. The results con rmed our hypothesis, showing the three-dimensionality of Customer Satisfaction. We found that reliability of tests' results, responsiveness of services and laboratory personnel's willingness to help have a signi cant in uence on customer satisfaction. The new customer satisfaction measurement scales model showed good reliability and factor-based and construct validity. The authors encourage practitioners and researchers to use this instrument for various applications, particularly in customer satisfaction surveys.

Managerial and theoretical implications
The above conclusion provides valuable practical and managerial implications for researchers and laboratory managers. It highlights principal areas where managerial attention is required for improving customer satisfaction. It is important for clinical laboratory managers to consider customer satisfaction with laboratory services as a multidimensional construct, where reliability of tests' results, responsiveness of services and laboratory personnel's willingness to help are important, because focusing only on one or another service quality is too narrow approach. We recommend that the laboratory develop a program to measure service quality and customer satisfaction on regular basis to meet the changing trend of customer tastes and preferences. The present study has some theoretical implications as well. This paper, being the rst study to attempt a comprehensive psychometric validation of an instrument that measures customer satisfaction with clinical laboratory services in DRC, has contributed to lling the gap in the literature. Additionally, ndings on the service quality dimensions that are of highest importance to customers are still subjective, and the current study theoretically contributes to increasing the knowledge insight in the eld of marketing.

Declarations
Ethics approval and consent to participate Before implementing the study, ethical clearance was obtained from the ethical review committee of the Public Health School, University of Kinshasa. The respondents were informed of the purpose of the study and assured of con dentiality and their right to withdraw from the study. Verbal consent was obtained after the study objectives were explained to each participant. Informed consent was obtained from each respondent, and con dentiality was maintained throughout the study.

Consent for publication
Not applicable Availability of data and materials The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests.