Total Clinical Chemistry Laboratory Errors and Evaluation of the Analytical Quality Control Using Sigma Metric for Routine Clinical Chemistry Tests

Figures & data

Table 1 Frequency of Missed Information on Laboratory Request Forms

S. No.	Variables	Missed Information
		%(Error/Total)
1	MRN	0(0/4719)
2	Patient age	26.9(1271/4719)
3	Gender of patient	24.1(1138/4719)
4	Signature of the physician	77.5(3658/4719)
5	Clinical history of the patient	100(4719/4719)
6	Location of the patient (Clinic/ward)	66.2(3122/4719)
7	Date of ordered	57.5(2715/4719)
8	Test ordered	0(0/4719)
9	Appropriate and authorized requests	1.7(80/4719)
Total		39.3(16,703/42,471)

Abbreviation: MRN, medical record number.

Table 2 Analysis of Errors in Pre-Analytical Quality Indicators

S. No.	Variables	Pre-Analytical Errors
		%(Error/Total)	% Total Errors
1	Hemolyzed specimen	2.4(111/4719)	35.4
2	Icteric specimen	2.1(97/4719)	30.9
3	Mislabeled specimen	1(45/4719)	14.3
4	Lipemic specimen	0.5(25/4719)	8
5	Inadequate specimen	0.3(14/4719)	4.5
6	Clotted sample	0.3(13/4719)	4.1
7	Specimen collected at wrong time	0.2(8/4719)	2.5
8	Test tube broken in the centrifuge	0.02(1/4719)	0.3
9	Specimen collected with wrong test tube	0(0/4719)	0
10	Specimen without its request	0(0/4719)	0
11	Specimen collected for unavailable test	0(0/4719)	0
Overall rejection rate of specimens		4.7(223/4719)
Total pre-analytical errors from all pre analytical QIs (Including laboratory test requests form and specimens)		18(17,017/94,380)

Abbreviation: QIs, quality indicators.

Table 3 Analysis of Errors in Analytical Quality Indicators

S. No.	Variables	Analytical Error
		%(Error/Total)
1	Non-linear results released without retesting	100(38/38)
2	Questionable results contradicted	100(28/28)
3	EQC failed	23.1(15/65)
4	Preventive maintenance not performed	16.7(9/54)
5	Equipment malfunction	9.1(4/44)
6	Reference range not available	6.3(1/16)
7	Laboratory fail to establish linearity range	6.3(1/16)
8	IQC result failed	6.2(81/1317)
9	Failure to perform daily IQC	5.3(73/1382)
10	Working reagents prepared incorrectly	4.5(4/88)
11	Electric interruption	3(141/4719)
12	Reagent stock out during analysis	1.3(62/4719)
13	Calibration failed	0(0/13)
14	Methods not updated upon new reagent	0(0/16)
15	Reagents used after their expiration date	0(0/691)
Total Errors from all analytical QIs		3.5(457/13,206)

Abbreviations: EQC, external quality control; IQC, internal quality control; QIs, quality indicators.

Table 4 Analysis of Errors in Post-Analytical Quality Indicators

S. No.	Variables	Post-Analytical Error
		%(Error/Total)
1	Requests released without result verification	99.5(4694/4719)
2	Critical values not communicated immediately	13.3(6/45)
3	Unrecorded test results	1.3(62/4719)
4	Results released out of TAT	1.1(53/4719)
5	All tests not performed as requested	0.2(8/4719)
6	Result printouts attached to the wrong request	0.1(4/4719)
7	Left over samples not retained as the policy	0(0/4719)
8	Laboratory requests with results lost	0(0/4719)
9	Request with incorrect unit of reporting	0(0/4719)
Total Errors from all post analytical QIs		12.8(4827/37,797)

Abbreviations: TAT, turnaround time; QIs, quality indicators.

Table 5 Distribution of Errors Frequency in the Total Testing Process

Phase	Error		% Total Errors	% Errors	Chi Square Test
	Yes	No
Pre-analytical	17,017	77,363	11.7	76.3	χ2	df	p-value
Analytical	457	12,749	0.3	2.1	2153	2	<0.0001
Post-analytical	4827	32,970	3.3	21.6
Total	22,301	123,082	15.3	100

Table 6 Association of Patient Location with Pre-Analytical and Post-Analytical Errors

Variables	Location of Patients (Clinic/Ward)								Test of Significance χ2 (p-Value)
	Emergency		OPD		IPD		Unknown
	Yes	No	Yes	No	Yes	No	Yes	No
Patient age missed	9	144	116	763	21	524	1125	2017	392*(p<0.0001)
Gender of patient missed	5	148	72	807	17	528	1044	2098	432*(p<0.0001)
Signature of the physicians missed	69	84	599	280	318	227	2672	470	353.5*(p<0.0001)
Location of the patient missed	5	148	6	873	8	537	3103	39	4463.5*(p<0.0001)
Date of ordered missed	62	91	335	544	161	384	2157	985	487.5*(p<0.0001)
Unauthorized requests	0	153	9	870	1	544	70	3072	17.8*(p<0.0001)
Hemolyzed specimen	6	147	17	862	21	524	67	3075	8.3*(p=0.04)
Icteric specimen	4	149	9	870	23	522	61	3081	17.77*(p<0.0001)
Mislabeled specimen	1	152	4	875	3	542	37	3105	5.06(p=0.167)
Specimen rejection	9	144	31	848	43	502	140	3002	15.9*(p=0.001)
Unrecorded results	1	152	21	858	9	536	31	3111	11.4*(p=0.010)
Results released out of TAT	3	150	14	865	10	535	26	3116	7.67(p=0.053)

Note: *Statistically significant association (p<0.05).

Abbreviations: IPD, impatient department; OPD, outpatient department; TAT, turnaround time.

Table 7 Factors Associated with Prolonged TAT

Variable	Category	Prolonged TAT		COR(95% CI)	AOR(95% CI)	p-Value
		Yes	No
Clinic/ward	Emergency	3	150	1.66(0.49–5.63)	1.66(0.49–5.63)	0.412
	OPD	14	865	1.596(0.82–3.09)	1.596(0.82–3.09)	0.165
	IPD	10	535	1.58(0.75–3.34)	1.59(0.75–3.34)	0.224
	Unknown	26	3116	1	1
Shift	1st shift	13	3410	1	1
	2nd shift	40	1256	7.83(4.15–14.77)	8.35(4.45–15.67)	<0.001

Note: p < 0.05= significant association.

Abbreviations: AOR, adjusted odds ratio; CI, confidence interval; COR, crude odds ratio; IPD, impatient department; OPD, outpatient department; TAT, turnaround time.

Table 8 Total Allowable Error (TEa), CV, Bias, Sigma Value and QGI of the Routine Clinical Chemistry Tests

Analyte	IQC Level	TEa%	Average Bias (%)	CV (%)	Sigma	QGI	Problem
AST	I	20	7.4	10.6	1.2	0.46	Imprecision
	II	20	7.4	6	2.1	0.82	Imprecision and inaccuracy
ALT	I	20	4.2	9.6	1.6	0.3	Imprecision
	II	20	4.2	7	2.3	0.4	Imprecision
ALP	I	30	2.7	7	3.9	0.26	Imprecision
	II	30	2.7	7.2	3.8	0.3	Imprecision
UR	I	19	7	8.6	1.4	0.54	Imprecision
	II	19	7	6.8	1.8	0.7	Imprecision
CRE	I	15	5	7.2	1.4	0.46	Imprecision
	II	15	5	6.6	1.5	0.5	Imprecision
GLU	I	10	5.4	7.6	0.6	0.47	Imprecision
	II	10	5.4	5.6	0.8	0.6	Imprecision
TC	I	10	4	7.6	0.8	0.35	Imprecision
	II	10	4	7.2	0.8	0.4	Imprecision
TG	I	15	13.7	11.8	0.1	0.77	Imprecision
	II	15	13.7	16	0.1	0.6	Imprecision
HDL	I	20	18.7	18.9	0.1	0.7	Imprecision
	II	20	18.7	10.8	0.1	1.1	Imprecision and Inaccuracy
LDL	I	20	19.8	6	0.03	2.2	Inaccuracy
	II	20	2.6	18.4	0.9	0.1	Imprecision
TP	I	10	6.3	5.9	0.6	0.7	Imprecision
	II	10	6.3	4.2	0.9	1	Imprecision and inaccuracy
ALB	I	10	9.9	7.2	0.01	0.9	Imprecision and inaccuracy
	II	10	9.9	6.2	0.02	1	Imprecision and inaccuracy
TBIL	I	20	9.9	7.4	1.4	0.9	Imprecision and inaccuracy
	II	20	9.9	6	1.7	1.1	Imprecision and inaccuracy
UA	I	17	6.3	8.3	1.3	0.5	Imprecision
	II	17	6.3	5.7	1.9	0.7	Imprecision

Abbreviations: CV, coefficient of variation; EQC, external quality control; IQC, internal quality control; QGI, quality goal index ratio; TE, total observed error; TEa, total allowable error.

Table 9 Quality Control Strategy Based on the Sigma Value of the Test Parameters

Parameters	Sigma Metrics	Levels of Control	Run	Westgard Rules	Status of the Method	Decision
AST, ALT, UR, CRE, GLU, TC, TG, HDL. LDL, TP, ALB, TBIL, UA	<3	–	–	–	Poor	Needs rechecking
ALP	3.8	2	4	13S/22S/R4S/41S/10x	Good	Acceptable

Note: No Westgard rule, IQC level and runs selected rather immediate trouble shooting requires.