Predicting return to work among sickness-certified patients in general practice: Properties of two assessment tools

Figures & data

Figure 1. Nomograms showing proportion (%) returning to work on day 28 (a), 90 (b), and day 180 (c) from baseline. Age is attained age at baseline, sick-leave days during the last year are the total number of days of sick-leave, and ICD-10 diagnostic codes are the ICD-10 chapter codes F = psychiatric disease, G = nervous system disease, I = cardiovascular disease, K = gastrointestinal disease, M = musculoskeletal disease, A = infectious disease, B = parasite disease, O = obstetric disorders, L = dermatology disease, N = genitourinary system diseases, H = eye or ear disease, J = respiratory disease. The return to work probability is obtained by drawing a line connecting the actual age and the number of sick-leave days last year. Where the line crosses the bold vertical line in the middle of the nomogram, the return to work probability (%) is found by moving horizontally to the sick-leave diagnosis group. For example, the proportion returning to work within the first 28 days in a 54-year-old subject with 73 sick-leave days last year and an F diagnosis is approximately 38%, and 78% if the diagnosis was J. The corresponding proportions at day 90 are approximately 56% and 92%, respectively.

Table I. Characteristics of the study population.

	Women		Men
	n	Mean (SD) or %	n	Mean (SD) or %
Age, years
Mean	482	39.1 (12.04)	461	39.2 (11.66)
Interquartile range		29–49		30–48
Employed, %	365	75.7	356	77.2
Marital status, %
Never married	195	40.5	218	47.3
Married or cohabiting	183	38.0	162	35.1
Divorced	90	18.7	79	17.1
Widowed	12	2.5	2	0.4
Sick-leave before baseline, days
Mean		55.1 (105.82)		48.8 (94.69)
Interquartile range		0–49		0–37
Full-time sick-leave at baseline	431	89.4	430	93.3
Sick-leave diagnoses (ICD-10), %
Musculoskeletal disease (M)	150	31.1	152	33.0
Psychiatric disease (F)	131	27.2	90	19.5
Respiratory disease (J)	88	18.3	70	15.2
Injury, poisoning (S, T)	17	3.5	34	7.4
Symptoms and signs (R)	33	6.9	31	6.7
Infectious-parasite disease (A, B)	12	2.5	20	4.3
Dermatology disease (L)	9	1.9	9	2.0
Cardiovascular disease (I)	8	1.7	10	2.2
Genitourinary system disease (N)	7	1.5	8	1.7
Digestive system disease (K)	5	1.0	13	2.8
Eye or ear disease (H)	5	1.0	6	1.3
Nervous system disease (G)	5	1.0	5	1.1
Endocrine-metabolic disease (E)	4	0.8	3	0.7
Blood disease (D)	3	0.6	1	0.2
Pregnancy, childbirth (O)	1	0.2	0	–
Miscellaneous	4	0.8	9	2.0

Table II. Characteristics of the risk groups and effects of the risk grouping on return to work.

	Low-risk group			High-risk group
	n	Mean (SD) or %	HR (95% CI)	n	Mean (SD) or %	HR (95% CI)	p for group difference
n	496	52.6		447	47.4
Age, years		38.2 (12.6)			40.2 (10.9)		< 0.005
Women, %	233	47.0		249	55.7		< 0.01
Employed, %	440	88.7		281	62.9		< 0.0001
Full-time sick-leave, %	481	97.0		380	85.0		< 0.0001
Sick-leave >28 days last year, %	68	13.7		210	47.0		< 0.0001
Sick-leave diagnosis
Musculoskeletal disorder	111	22.4		191	42.7		< 0.0001
Psychiatric disorder	59	11.9		162	36.2		< 0.0001
Effect on return to work
Within 28 days	435	87.7	1.00 –	181	40.5	0.29 (0.24–0.34)	< 0.0001
Within 90 days	466	94.0	1.00 –	275	61.5	0.32 (0.28–0.38)	< 0.0001
Within 180 days	479	96.6	1.00 –	331	74.1	0.35 (0.30–0.40)	< 0.0001

Differences in characteristics were tested with Student’s t test, and effect on return to work with proportional hazards regression.

Table III. Effects of possible determinants on return to work during three time periods.

	Return to work
	HR	95% CI	Wald’s chi-square	p	Concordance c index
First 28 days					86.1
Age, years	0.987	0.981–0.994	13.0	< 0.0005
Sick-leave last year, days	0.990	0.987–0.992	87.2	< 0.0001
Full-time sick-leave	0.45	0.29–0.68	13.8	< 0.0005
Sick-leave diagnosis
F or G –2	0.35	0.27–0.45	66.6	< 0.0001
I, K, or M –1	0.48	0.38–0.60	44.7	< 0.0001
All other diagnoses (0)	0.59	0.46–0.75	17.2	< 0.0001
A, B, O, L (+1)	0.69	0.50–0.97	4.7	< 0.05
N (+2)	1.00	0.56–1.81	0	0.99
First 90 days					88.0
Age, years	0.983	0.977–0.989	27.8	< 0.0001
Sick-leave last year, days	0.992	0.981–0.993	128.3	< 0.0001
Full-time sick-leave	0.59	0.43–0.80	11.3	< 0.001
Sick-leave diagnosis
F or G –2	0.35	0.27–0.44	81.2	< 0.0001
I, K, or M –1	0.44	0.35–0.54	61.4	< 0.0001
All other diagnoses (0)	0.53	0.42–0.68	26.1	< 0.0001
A, B, O, L (+1)	0.67	0.48–0.92	6.0	< 0.05
N (+2)	1.03	0.58–1.82	0	0.92
First 180 days					89.4
Age, years	0.982	0.976–0.988	32.9	< 0.0001
Sick-leave last year, days	0.993	0.992–0.994	153.6	< 0.0001
Full-time sick-leave	0.73	0.56–0.95	5.4	< 0.05
Sick-leave diagnosis
F or G –2	0.33	0.27–0.42	91.9	< 0.0001
I, K, or M –1	0.43	0.35–0.53	65.9	< 0.0001
All other diagnoses (0)	0.52	0.41–0.66	28.9	< 0.0001
A, B, O, L (+1)	0.67	0.49–0.93	5.8	< 0.05
N (+2)	0.99	0.56–1.74	0	0.96